\input texinfo    @c -*- texinfo -*-
@c %**start of header
@setfilename ghub.info
@settitle Ghub User and Developer Manual
@documentencoding UTF-8
@documentlanguage en
@c %**end of header

@copying
@quotation
Copyright (C) 2017-2018 Jonas Bernoulli <jonas@@bernoul.li>

You can redistribute this document and/or modify it under the terms
of the GNU General Public License as published by the Free Software
Foundation, either version 3 of the License, or (at your option) any
later version.

This document is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE@.  See the GNU
General Public License for more details.

@end quotation
@end copying

@dircategory Emacs
@direntry
* Ghub: (ghub).         Minuscule client library for the Github API.
@end direntry

@finalout
@titlepage
@title Ghub User and Developer Manual
@subtitle for version 3.0.0 (v3.0.0-11-gca1982d+1)
@author Jonas Bernoulli
@page
@vskip 0pt plus 1filll
@insertcopying
@end titlepage

@contents

@ifnottex
@node Top
@top Ghub User and Developer Manual

Ghub provides basic support for using the APIs of various Git forges
from Emacs packages.  Originally it only supported the Github REST
API, but now it also supports the Github GraphQL API as well as the
REST APIs of Gitlab, Gitea, Gogs and Bitbucket.

Ghub abstracts access to API resources using only a handful of basic
functions such as `ghub-get`.  These are convenience wrappers around
`ghub-request`.  Additional forge-specific wrappers like `glab-put`,
`gtea-put`, `gogs-post` and `buck-delete` are also available.  Ghub
does not provide any resource-specific functions, with the exception
of `FORGE-repository-id`.

When accessing Github, then Ghub handles the creation and storage of
access tokens using a setup wizard to make it easier for users to get
started.  The tokens for other forges have to be created manually.

Ghub is intentionally limited to only provide these two essential
features — basic request functions and guided setup — to avoid being
too opinionated, which would hinder wide adoption.  It is assumed that
wide adoption would make life easier for users and maintainers alike,
because then all packages that talk to forge APIs could be configured
the same way.

@noindent
This manual is for Ghub version 3.0.0 (v3.0.0-11-gca1982d+1).

@quotation
Copyright (C) 2017-2018 Jonas Bernoulli <jonas@@bernoul.li>

You can redistribute this document and/or modify it under the terms
of the GNU General Public License as published by the Free Software
Foundation, either version 3 of the License, or (at your option) any
later version.

This document is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE@.  See the GNU
General Public License for more details.

@end quotation
@end ifnottex

@menu
* Introduction::
* Getting Started::
* Using Ghub in Personal Scripts::
* Using Ghub in a Package::
* API::
* GraphQL Support::
* Support for Other Forges::

@detailmenu
--- The Detailed Node Listing ---

Getting Started

* Setting the Username::
* Interactively Creating and Storing a Token::
* Manually Creating and Storing a Token::
* How Ghub uses Auth-Source::

API

* Making Requests::
* Authentication::
* Configuration Variables::

Support for Other Forges

* Forge Functions and Variables::
* Forge Limitations and Notes::

@end detailmenu
@end menu

@node Introduction
@chapter Introduction

Ghub provides basic support for using the APIs of various Git forges
from Emacs packages.  Originally it only supported the Github REST
API, but now it also supports the Github GraphQL API as well as the
REST APIs of Gitlab, Gitea, Gogs and Bitbucket.

Ghub abstracts access to API resources using only a handful of basic
functions such as `ghub-get`.  These are convenience wrappers around
`ghub-request`.  Additional forge-specific wrappers like `glab-put`,
`gtea-put`, `gogs-post` and `buck-delete` are also available.  Ghub
does not provide any resource-specific functions, with the exception
of `FORGE-repository-id`.

When accessing Github, then Ghub handles the creation and storage of
access tokens using a setup wizard to make it easier for users to get
started.  The tokens for other forges have to be created manually.

Ghub is intentionally limited to only provide these two essential
features — basic request functions and guided setup — to avoid being
too opinionated, which would hinder wide adoption.  It is assumed that
wide adoption would make life easier for users and maintainers alike,
because then all packages that talk to forge APIs could be configured
the same way.

Fancier interfaces can be implemented on top of Ghub, and one such
wrapper — named simply Ghub+ — has already been implemented.  The
benefit of basing various opinionated interfaces on top of a single
library that provides only the core functionality is that choosing the
programming interface no longer dictates how access tokens are
handled.  Users can then use multiple packages that access the Github
API without having to learn the various incompatible ways packages
expect the appropriate token to be made available to them.

Ghub uses the built-in @code{auth-source} library to store access tokens.
That library is very flexible and supports multiple backends, which
means that it is up to the user how secrets are stored.  They can,
among other things, choose between storing secrets in plain text for
ease of use, or encrypted for better security.

Previously (as in until this library is widely adopted) it was up to
package authors to decide if things should be easy or secure.  (Note
that @code{auth-source} defaults to "easy" — you have been warned.)

Ghub expects package authors to use a dedicated access token instead
of sharing a single token between all packages that rely on it.  That
means that users cannot configure Ghub once and later start using a
new package without any additional setup.  But Ghub helps with that.

When the user invokes some command that ultimately results in
@code{ghub-request} being called and the appropriate token is not available
yet, then the user is guided through the process of creating and
storing a new token, and at the end of that process the request is
carried out as if the token had been available to begin with.

@node Getting Started
@chapter Getting Started

Each package that uses Ghub uses its own token.  Despite that, chances
are good that after successfully configuring one package you can just
start using another package pretty much instantly.

If the necessary token to access a Github instance is not available
when a package makes an API request, then a setup wizard pops up, and
after answering a few questions you are good to go.  Even the request
that caused the wizard to be summoned should succeed and for most
users this should be true even when configuring the very first token.

However, in some situations some manual configuration is necessary
@strong{before} using the wizard, or the wizard cannot be used at all:

@itemize
@item
If you don't want to use the wizard then you don't have to and can
create tokens manually as described in @ref{Manually Creating and Storing a Token}.


@item
Unfortunately only Github supports the creation of tokens by using
the API@.  If you want to access another forge, then you have to
create the token manually as describe in @ref{Manually Creating and Storing a Token}.  Also see @ref{Support for Other Forges}.


@item
If you want to access a Github Enterprise instance, then you have
to tell Ghub about that before the wizard makes its appearance by
setting the Git variable @code{github.host}.  You also have to tell Ghub
your username for that instance using the variable @code{github.HOST.user}
even if it is the same as on Github.com.

These variables are documented in @ref{Configuration Variables}. Also see
@ref{Setting the Username}.  TL;DR: If your Github Enterprise instance is
hosted at @code{git.example.com} and your username on that instance is
@code{jtribbiani}, then set @code{github.host} to @code{git.example.com/api/v3} in every
repository cloned from that instance (i.e. @emph{do not} set it globally)
and @emph{globally} set @code{github.git.example.com/api/v3.user} to @code{jtribbiani}.
The latter is necessary even if your username on Github.com is the
same.


@item
If the variable @code{github.user} (or @code{github.HOST.user} for an Enterprise
instance) is unset when the wizard is first summoned, then you are
asked to provide your username.  That value is then stored @strong{globally}
to avoid having to ask you that question once per repository.  If
you have multiple accounts on Github.com (or a Github Enterprise
instance), then you have to explicitly tell Ghub about that.  This
can be done by setting the repository-local values of the
appropriate variable @strong{before} the wizard is invoked.


@item
You might forget to do the above, which is why it is important to
carefully read the output of the wizard.  If it turns out that you
forgot to set a variable, then you must abort, set the variable, and
repeat the request to trigger the wizard again.


@item
The setup wizard should work even if you have enabled two-factor
authentication.  However if your Github Enterprise instance enforces
Single Sign-On as an additional security measure, then you are out
of luck and have to create the token manually as described in
@ref{Manually Creating and Storing a Token}.
@end itemize

The variables mentioned above — and others — are documented in
@ref{Configuration Variables} and the setup wizard is documented in
@ref{Interactively Creating and Storing a Token}.

@menu
* Setting the Username::
* Interactively Creating and Storing a Token::
* Manually Creating and Storing a Token::
* How Ghub uses Auth-Source::
@end menu

@node Setting the Username
@section Setting the Username

If you haven't set the Git variable @code{github.user} yet when making a
request, then you will be asked:

@example
Git variable `github.user' is unset.  Set to:
@end example

You are expected to provide your Github username here.  The provided
value will be saved globally (using @code{git config --global github.user
USERNAME}).

If you need to identify as another user in a particular repository,
then you have to set that variable locally, @strong{before} making a request:

@example
cd /path/to/repo
git config github.user USERNAME
@end example

For Github Enterprise instances you have to specify where the API can
be accessed @strong{before} you try to access it and a different variable has
to be used to set the username.  For example if the API is available
at @code{https://example.com/api/v3}, then you should do this:

@example
# Do this once
git config --global github.example.com/api/v3.user EMPLOYEE

# Do this for every corporate repository
cd /path/to/repo
git config github.host example.com/api/v3
@end example

If you do not set @code{github.example.com/api/v3.user}, then you will be
asked to provide the value when trying to make a request, but you do
have to manually set @code{github.host}, or Ghub assumes that you are trying
to access @code{api.github.com}.

@node Interactively Creating and Storing a Token
@section Interactively Creating and Storing a Token

Ghub uses a different token for every package as well as for every
machine from which you access the Github API (and obviously also for
every Github instance and user).  This allows packages to only request
the scopes that they actually need and also gives users the
opportunity to refuse access to certain scopes if they expect to not
use the features that need them.

Usually you don't have to worry about creating and storing a token
yourself and can just make a request.  Note however that you don't
have to use the setup wizard described below.  Alternatively you can
perform the setup manually as described in the next section.

If you make a request and the required token is not available yet,
then the setup wizard will first ask you something like this:

@example
Such a Github API token is not available:

  Host:    api.github.com
  User:    USERNAME
  Package: PACKAGE

  Scopes requested in `PACKAGE-github-token-scopes':
    repo
  Store on Github as:
    "Emacs package PACKAGE @@ LOCAL-MACHINE"
  Store locally according to option `auth-sources':
    ("~/.authinfo" "~/.authinfo.gpg" "~/.netrc")

If in doubt, then abort and first view the section of
the Ghub documentation called "Interactively Creating
and Storing a Token".

Create and store such a token? (yes or no)
@end example

If you don't have any doubts, then answer "yes".  Lets address some
of the doubts that you might have:

@itemize
@item
@code{Host} usually is "api.github.com" and that is usually what you want.
If you are trying to access a Github Enterprise instance, then it
should be something else and you have to set the value manually
before the setup wizard is summoned, as described in the parent
section.


@item
@code{User} should be your Github.com (or Github Enterprise instance)
username.  If it is something else and it doesn't look like a simple
typo, then you should read the parent section again.  In either case
you have to abort.


@item
@code{Package} should be the name of the package you are using to access
the Github API@.

If it is @code{ghub}, then the package author disregarded that convention
and you should probably report a bug in the issue tracker of that
package.

Or you yourself are using @code{ghub-request} or one of its wrappers
directly, in which case this is expected and perfectly fine.  In
that case you might however want to abort and change the value of
the variable @code{ghub-github-token-scopes} before triggering the wizard
again.


@item
Each @code{PACKAGE} has to specify the tokens that it needs using a
variable named @code{PACKAGE-github-token-scopes}.  The doc-string of
that variable should document why the various scopes are needed.

The meaning of the various scopes are documented at
@uref{https://magit.vc/goto/f63aeb0a}.


@item
The value of @code{auth-sources} is shown.  The default value causes
secrets to be stored in plain text.  Because this might be
unexpected, Ghub additionally displays a warning when appropriate.

@example
WARNING: The token will be stored unencrypted in "~/.authinfo".
         If you don't want that, you have to abort and customize
         the `auth-sources' option.
@end example

Whether that is something that needs fixing, is up to you.  If your
answer is yes, then you should abort and see @ref{How Ghub uses Auth-Source} for instructions on how to save the token more securely.


@item
When creating a token it is necessary to provide a token
description.  Ghub uses descriptions that have the form "Emacs
package PACKAGE @@ LOCAL-MACHINE".

Github uses the token description to identify the token, not merely
as something useful to humans.  Token descriptions therefore have to
be unique and in rare cases you get an additional prompt, asking you
something like:

@example
A token named "Emacs package PACKAGE @@ LOCAL-MACHINE"
already exists on Github.  Replace it?
@end example

You might see this message when you have lost the old token and want
to replace it with a new one, in which case you should obviously just
proceed.

Or two of your computers have the same hostname, which is bad
practice because it gains you nothing but leads to issues such as
this.  Or you are dual-booting on this machine and use the same
hostname in all operating systems, which is a somewhat reasonable
thing to do, but never-the-less leads to issues like this.

In either case you will have to use something other than the value
returned by @code{system-name} to identify the current machine or operating
system.  Or you can continue to identify different things using the
same identifier, in which case you have to manually distribute the
token.

The former is recommended and also easier to do, using the variable
@code{ghub-override-system-name}.  See @ref{Configuration Variables} for
details.
@end itemize

After the above prompt you are also asked for your username and
password.  If you have enabled two-factor authentication, then you
also have to provide the authentication code at least twice.  If you
make sure the code is still good for a while when asked for it first,
then you can just press @code{RET} at the later prompt(s).

@node Manually Creating and Storing a Token
@section Manually Creating and Storing a Token

If you cannot or don't want to use the wizard then you have to (1)
figure out what scopes a package wants, (2) create such a token using
the web interface and (3) store the token where Ghub expects to find
it.

A package named @code{PACKAGE} has to specify the scopes that it wants in
the variable named @code{PACKAGE-ghub-token-scopes}.  The doc-string of
such variables should document what the various scopes are needed for.

To create or edit a token go to @uref{https://github.com/settings/tokens}.
For Gitlab.com use @uref{https://gitlab.com/profile/personal_access_tokens}.

Finally store the token in a place where Ghub looks for it, as
described in @ref{How Ghub uses Auth-Source}.

If you store the token in a file like @code{~/.authinfo}, then note that
@code{auth-source}'s parsing of that file is brittle.  Make sure the file
ends with a newline character, that there are no empty or invalid
lines, and that all comments are prefixed with @code{#}.

@node How Ghub uses Auth-Source
@section How Ghub uses Auth-Source

Please see @ref{Top,,,auth,} for all the gory details about Auth-Source.
Some Ghub-specific information and important notes follow.

The variable @code{auth-sources} controls how and where Auth-Source stores
new secrets and where it looks for known secrets.  The default value
is @code{("~/.authinfo" "~/.authinfo.gpg" "~/.netrc")}, which means that it
looks in all of these files in order to find secrets and that it
stores new secrets in @code{~/.authinfo} because that is the first element of
the list.  It doesn't matter which files already do or don't exist
when storing a new secret, the first file is always used.

Secrets are stored in @code{~/.authinfo} in plain text.  If you don't want
that (good choice), then you have to customize @code{auth-sources}, e.g. by
flipping the positions of the first two elements.

Auth-Source also supports storing secrets in various key-chains.
Refer to its documentation for more information.

Some Auth-Source backends only support storing three values per entry,
the "machine", the "login" and the "password".  Because Ghub uses
separate tokens for each package, it has to squeeze four values into
those three slots, and it does that by using "USERNAME@math{^PACKAGE}" as the
"login".

Assuming your username is "ziggy",the package is named "stardust", and
you want to access @strong{Github.com} an entry in one of the three mentioned
files would then look like this:

@example
machine api.github.com login ziggy^stardust password 012345abcdef...
@end example

Assuming your username is "ziggy",the package is named "stardust", and
you want to access @strong{Gitlab.com} an entry in one of the three mentioned
files would then look like this:

@example
machine gitlab.com/api/v4 login ziggy^stardust password 012345abcdef...
@end example

@node Using Ghub in Personal Scripts
@chapter Using Ghub in Personal Scripts

You can use @code{ghub-request} and its wrapper functions in your personal
scripts, of course.  Unlike when you use Ghub from a package that you
distribute for others to use, you don't have to specify a package in
personal scripts.

@lisp
;; This is perfectly acceptable in personal scripts ...
(ghub-get "/user")

;; ... and actually equal to
(ghub-get "/user" nil :auth 'ghub)

;; In packages you have to specify the package using AUTH.
(ghub-get "/user" nil :auth 'foobar)
@end lisp

When you do not specify the @code{AUTH} argument, then a request is made on
behalf of the @code{ghub} package itself.  Like for any package that uses
Ghub, @code{ghub} has to declare what scopes it needs, using, in this case,
the variable @code{ghub-github-token-scopes}.

The default value of that variable is @code{(repo)} and you might want to add
additional scopes.  You can later add additional scopes to an existing
token, using the web interface at @uref{https://github.com/settings/tokens}.

If you do that, then you might want to also set the variable
accordingly, but note that Ghub only consults that when @strong{creating} a new
token.  If you want to know a token's effective scopes use the command
@code{ghub-token-scopes}, described in the next section.

@node Using Ghub in a Package
@chapter Using Ghub in a Package

Every package should use its own token.  This allows you as the author
of some package to only request access to API scopes that are actually
needed, which in turn might make it easier for users to trust your
package not to do unwanted things.

The scopes used by @code{PACKAGE} have to be defined using the variable
@code{PACKAGE-github-token-scopes}, and you have to tell @code{ghub-request} on
behalf of which package a request is being made by passing the symbol
@code{PACKAGE} as the value of its @code{AUTH} argument.

@lisp
(ghub-request "GET" "/user" nil :auth 'PACKAGE)
@end lisp

@defvar PACKAGE-github-token-scopes

This variable defines the token scopes requested by the package
named @code{PACKAGE}.  The doc-string should explain what the various
scopes are needed for to prevent users from giving @code{PACKAGE} fewer
permissions than it absolutely needs and also to give them greater
confidence that @code{PACKAGE} is only requesting the permissions that it
actually needs.

The value of this variable does not necessarily correspond to the
scopes that the respective token actually gives access to.  There is
nothing that prevents users from changing the value @strong{after} creating
the token or from editing the token's scopes later on.

So it is pointless to check the value of this variable before making
a request.  You also should not query the API to reliably determine
the supported tokens before making a query.  Doing the latter would
mean that every request becomes two requests and that the first
request would have to be done using the user's password instead of a
token.
@end defvar

@cindex ghub-token-scopes
@deffn Command ghub-token-scopes

Because we cannot be certain that the user hasn't messed up the
scopes, Ghub provides this command to make it easy to debug such
issues without having to rely on users being thoughtful enough to
correctly determine the used scopes manually.

Just tell users to run @code{M-x ghub-token-scopes} and to provide the
correct values for the @code{HOST}, @code{USERNAME} and @code{PACKAGE} when
prompted, and to then post the output.

It is to be expected that users will occasionally mess that up so
this command outputs not only the scopes but also the user input so
that you can have greater confidence in the validity of the user's
answer.

@example
Scopes for USERNAME^PACKAGE@@HOST: (SCOPE...)
@end example
@end deffn

@node API
@chapter API

This section describes the Ghub API@.  In other words it describes the
public functions and variables provided by the Ghub package and not
the APIs of the supported forges, which can be accessed by using those
functions.  The forge APIs are documented at:

@itemize
@item
Github: @uref{https://developer.github.com/v3}

@item
Gitlab: @uref{https://docs.gitlab.com/ee/api/README.html}

@item
Gitea: @uref{https://docs.gitea.io/en-us/api-usage} and
@uref{https://try.gitea.io/api/swagger}

@item
Gogs: @uref{https://github.com/gogs/go-gogs-client/wiki}

@item
Bitbucket: @uref{https://developer.atlassian.com/bitbucket/api/2/reference}
@end itemize

@menu
* Making Requests::
* Authentication::
* Configuration Variables::
@end menu

@node Making Requests
@section Making Requests

@defun ghub-request method resource &optional params &key query payload headers unpaginate noerror reader username auth host callback errorback url value error extra method*

This function makes a request for @code{RESOURCE} using @code{METHOD}.
@code{PARAMS}, @code{QUERY}, @code{PAYLOAD} and/or @code{HEADERS} are alists holding
additional request data.  The response body is returned and the
response headers are stored in the variable @code{ghub-response-headers}.

@itemize
@item
@code{METHOD} is the HTTP method, given as a string.

@item
@code{RESOURCE} is the resource to access, given as a string beginning
with a slash.


@item
@code{PARAMS}, @code{QUERY}, @code{PAYLOAD} and @code{HEADERS} are alists and are used
to specify request data.  All these arguments are alists that
resemble the JSON expected and returned by the Github API@.  The
keys are symbols and the values stored in the @code{cdr} (not the
@code{cadr}) can be strings, integers, or lists of strings and
integers.

The Github API documentation is vague on how data has to be
transmitted and for a particular resource usually just talks about
"parameters".  Generally speaking when the @code{METHOD} is "HEAD" or
"GET", then they have to be transmitted as a query, otherwise as a
payload.

@itemize
@item
Use @code{PARAMS} to automatically transmit like @code{QUERY} or @code{PAYLOAD}
would depending on @code{METHOD}.

@item
Use @code{QUERY} to explicitly transmit data as a query.

@item
Use @code{PAYLOAD} to explicitly transmit data as a payload.  Instead
of an alist, @code{PAYLOAD} may also be a string, in which case it
gets encoded as UTF-8 but is otherwise transmitted as-is.

@item
Use @code{HEADERS} for those rare resources that require that the
data is transmitted as headers instead of as a query or payload.
When that is the case, then the Github API documentation usually
mentions it explicitly.
@end itemize


@item
If @code{SILENT} is non-nil, then progress reports and the like are not
messaged.


@item
If @code{UNPAGINATE} is t, then this function make as many requests as
necessary to get all values.  If @code{UNPAGINATE} is a natural number,
then it gets at most that many pages.  For any other non-nil value
it raises an error.


@item
If @code{NOERROR} is non-nil, then no error is raised if the request
fails and @code{nil} is returned instead.  If @code{NOERROR} is @code{return},
then the error payload is returned instead of @code{nil}.


@item
If @code{READER} is non-nil, then it is used to read and return from
the response buffer.  The default is @code{ghub--read-json-payload}.
For the very few resources that do not return JSON, you might want
to use @code{ghub--decode-payload}.


@item
If @code{USERNAME} is non-nil, then the request is made on behalf of
that user.  It is better to specify the user using the Git
variable @code{github.user} for "api.github.com", or @code{github.HOST.user}
if connecting to a Github Enterprise instance.


@item
Each package that uses Ghub should use its own token.  If @code{AUTH}
is @code{nil} or unspecified, then the generic @code{ghub} token is used
instead.  This is only acceptable for personal utilities.  A
packages that is distributed to other users should always use this
argument to identify itself, using a symbol matching its name.

Package authors who find this inconvenient should write a wrapper
around this function and possibly for the method-specific
functions as well.

Beside @code{nil}, some other symbols have a special meaning too.
@code{none} means to make an unauthorized request.  @code{basic} means to
make a password based request.  If the value is a string, then it
is assumed to be a valid token.  @code{basic} and an explicit token
string are only intended for internal and debugging uses.

If @code{AUTH} is a package symbol, then the scopes are specified using
the variable @code{AUTH-github-token-scopes}.  It is an error if that
is not specified.  See @code{ghub-github-token-scopes} for an example.


@item
If @code{HOST} is non-nil, then connect to that Github instance.
This defaults to "api.github.com".  When a repository is connected
to a Github Enterprise instance, then it is better to specify that
using the Git variable @code{github.host} instead of using this
argument.


@item
If @code{FORGE} is @code{gitlab}, then connect to Gitlab.com or, depending
on @code{HOST}, to another Gitlab instance.  This is only intended for
internal use.  Instead of using this argument you should use
function @code{glab-request} and other @code{glab-*} functions.


@item
If @code{CALLBACK} and/or @code{ERRORBACK} is non-nil, then this function makes
one or more asynchronous requests and calls @code{CALLBACK} or @code{ERRORBACK}
when finished.  If no error occurred, then it calls @code{CALLBACK},
unless that is @code{nil}.

If an error occurred, then it calls @code{ERRORBACK}, or if that is nil,
then @code{CALLBACK}.  @code{ERRORBACK} can also be @code{t}, in which case it signals
instead.  @code{NOERROR} is ignored for all asynchronous requests.

Both callbacks are called with four arguments.

@itemize
@item
For @code{CALLBACK}, the combined value of the retrieved pages.
For @code{ERRORBACK}, the error that occured when retrieving the
last page.

@item
The headers of the last page as an alist.

@item
Status information provided by @code{url-retrieve}.  Its @code{:error}
property holds the same information as the first argument to
@code{ERRORBACK}.

@item
A @code{ghub--req} struct, which can be passed to @code{ghub-continue}
(which see) to retrieve the next page, if any.
@end itemize
@end itemize
@end defun

@defun ghub-continue args

If there is a next page, then this function retrieves that.

This function is only intended to be called from callbacks.  If
there is a next page, then that is retrieved and the buffer that
the result will be loaded into is returned, or t if the process
has already completed.  If there is no next page, then return nil.

Callbacks are called with four arguments (see @code{ghub-request}).
The forth argument is a @code{ghub--req} struct, intended to be passed
to this function.  A callback may use the struct's @code{extra} slot
to pass additional information to the callback that will be called
after the next request.  Use the function @code{ghub-req-extra} to get
and set the value of that slot.

As an example, using @code{ghub-continue} in a callback like so:

@lisp
(ghub-get "/users/tarsius/repos" nil
          :callback (lambda (value _headers _status req)
                      (unless (ghub-continue req)
                        (setq my-value value))))
@end lisp

is equivalent to:

@lisp
(ghub-get "/users/tarsius/repos" nil
          :unpaginate t
          :callback (lambda (value _headers _status _req)
                      (setq my-value value)))
@end lisp

To demonstrate how to pass information from one callback to the
next, here we record when we start fetching each page:

@lisp
(ghub-get "/users/tarsius/repos" nil
          :extra (list (current-time))
          :callback (lambda (value _headers _status req)
                      (push (current-time) (ghub-req-extra req))
                      (unless (ghub-continue req)
                        (setq my-times (ghub-req-extra req))
                        (setq my-value value))))
@end lisp
@end defun

@defvar ghub-response-headers

A select few Github API resources respond by transmitting data in
the response header instead of in the response body.  Because there
are so few of these inconsistencies, @code{ghub-request} always returns
the response body.

To access the response headers use this variable after @code{ghub-request}
has returned.
@end defvar

@defun ghub-response-link-relations req headers payload

This function returns an alist of the link relations in @code{HEADERS}, or
if optional @code{HEADERS} is nil, then those in @code{ghub-response-headers}.

When accessing a Bitbucket instance then the link relations are in
@code{PAYLOAD} instead of @code{HEADERS}, making their API merely RESTish and
forcing this function to append those relations to the value of
@code{ghub-response-headers}, for later use when this function is called
with @code{nil} for @code{PAYLOAD}.
@end defun

@defvar ghub-override-system-name

If non-nil, the value of this variable is used to override the value
returned by @code{system-name} for the purpose of identifying the local
machine, which is necessary because Ghub uses separate tokens for
each machine.  Also see @ref{Configuration Variables}.
@end defvar

@defvar ghub-github-token-scopes
@end defvar
@defvar PACKAGE-github-token-scopes

Such a variable defines the token scopes requested by the respective
package @code{PACKAGE} given by the first word in the variable name.
@code{ghub} itself is treated like any other package.  Also see @ref{Using Ghub in a Package}.
@end defvar

@defun ghub-head resource &optional params &key query payload headers unpaginate noerror reader username auth host callback errorback
@end defun
@defun ghub-get resource &optional params &key query payload headers unpaginate noerror reader username auth host callback errorback

These functions are simple wrappers around @code{ghub-request}.  Their
signature is identical to that of the latter, except that they do
not have an argument named @code{METHOD}.  The HTTP method is instead
given by the second word in the function name.

As described in the documentation for @code{ghub-request}, it depends on
the used method whether the value of the @code{PARAMS} argument is used
as the query or the payload.  For the "HEAD" and "GET" methods it
is used as the query.
@end defun

@defun ghub-put resource &optional params &key query payload headers unpaginate noerror reader username auth host callback errorback
@end defun
@defun ghub-post resource &optional params &key query payload headers unpaginate noerror reader username auth host callback errorback
@end defun
@defun ghub-patch resource &optional params &key query payload headers unpaginate noerror reader username auth host callback errorback
@end defun
@defun ghub-delete resource &optional params &key query payload headers unpaginate noerror reader username auth host callback errorback

These functions are simple wrappers around @code{ghub-request}.  Their
signature is identical to that of the latter, except that they do
not have an argument named @code{METHOD}.  The HTTP method is instead
given by the second word in the function name.

As described in the documentation for @code{ghub-request}, it depends on
the used method whether the value of the @code{PARAMS} argument is used
as the query or the payload.  For the "PUT", "POST", "PATCH" and
"DELETE" methods it is used as the payload.
@end defun

@defun ghub-wait resource &optional duration &key username auth host

Some API requests result in an immediate successful response even
when the requested action has not actually been carried out yet.
An example is the request for the creation of a new repository,
which doesn't cause the repository to immediately become available.
The Github API documentation usually mentions this when describing
an affected resource.

If you want to do something with some resource right after making
a request for its creation, then you might have to wait for it to
actually be created.  This function can be used to do so.  It
repeatedly tries to access the resource until it becomes available
or until the timeout exceeds.  In the latter case it signals
@code{ghub-error}.

@code{RESOURCE} specifies the resource that this function waits for.

@code{DURATION} specifies the maximum number of seconds to wait for,
defaulting to 64 seconds.  Emacs will block during that time, but
the user can abort using @code{C-g}.

The first attempt is made immediately and will often succeed.  If
not, then another attempt is made after two seconds, and each
subsequent attempt is made after waiting as long as we already
waited between all preceding attempts combined.

See @code{ghub-request}'s documentation above for information about the
other arguments.
@end defun

@defun ghub-graphql graphql &optional variables &key username auth host callback

This function makes a GraphQL request using @code{GRAPHQL} and
@code{VARIABLES} as inputs.  @code{GRAPHQL} is a GraphQL string.  @code{VARIABLES}
is a JSON-like alist.  The other arguments behave as for
@code{ghub-request} (which see).

The response is returned as a JSON-like alist.  Even if the response
contains @code{errors}, this function does not raise an error.
Cursor-handling is likewise left to the caller.
@end defun

@node Authentication
@section Authentication

@cindex ghub-create-token
@deffn Command ghub-create-token

This command creates a new token using the values it reads from the
user and then stores it according to the variable @code{auth-sources}.
It can also be called non-interactively, but you shouldn't do that
yourself.

This is useful if you want to fully setup things before attempting
to make the initial request, if you want to provide fewer than the
requested scopes or customize @code{auth-sources} first, or if something
has gone wrong when using the wizard that is used when making a
request without doing this first.  (Note that instead of using this
command you can also just repeat the initial request after making
the desired adjustments — that is easier.)

This command reads, in order, the @code{HOST} (Github instance), the
@code{USERNAME}, the @code{PACKAGE}, and the @code{SCOPES} in the minibuffer,
providing reasonable default choices.  @code{SCOPES} defaults to the
scopes that @code{PACKAGE} requests using the variable
@code{PACKAGE-github-token-scopes}.
@end deffn

@cindex ghub-token-scopes
@deffn Command ghub-token-scopes

Users are free to give a token access to fewer scopes than what the
respective package requested.  That can, of course, lead to issues,
and package maintainers have to be able to quickly determine if such
a (mis-)configuration is the root cause when users report issues.

This command reads the required values in the minibuffer and then
shows a message containing these values along with the scopes of the
respective token.  It also returns the scopes (only) when called
non-interactively.  Also see @ref{Using Ghub in a Package}.
@end deffn

@node Configuration Variables
@section Configuration Variables

The username and, unless you only use Github.com itself, the Github
Enterprise instance have to be configured using Git variables.  In
rare cases it might also be necessary to specify the identity of the
local machine, which is done using a lisp variable.

@defvar github.user

The Github.com username.  This should be set globally and if you
have multiple Github.com user accounts, then you should set this
locally only for those repositories that you want to access using
the secondary identity.
@end defvar

@defvar github.HOST.user

This variable serves the same purpose as @code{github.user} but for the
Github Enterprise instance identified by @code{HOST}.

The reason why separate variables are used is that this makes it
possible to set both values globally instead of having to set one of
the values locally in each and every repository that is connected to
the Github Enterprise instance, not Github.com.
@end defvar

@defvar github.host

This variable should only be set locally for a repository and
specifies the Github Enterprise edition that that repository is
connected to.  You should not set this globally because then each
and every repository becomes connected to the specified Github
Enterprise instance, including those that should actually be
connected to Github.com.

When this is undefined, then "api.github.com" is used (defined in
the constant @code{ghub-default-host}, which you should never attempt to
change.)
@end defvar

@defvar ghub-override-system-name

Ghub uses a different token for each quadruple @code{(USERNAME PACKAGE
  HOST LOCAL-MACHINE)}.  Theoretically it could reuse tokens to some
extent but that would be more difficult to implement, less flexible,
and less secure (though slightly more convenient).

A token is identified on the respective Github instance (Github.com
or a Github Enterprise instance) using the pair @code{(PACKAGE .
  LOCAL-MACHINE)}, or more precisely the string "Emacs package PACKAGE
@@ LOCAL-MACHINE".  @code{USERNAME} and @code{HOST} do not have to be encoded
because the token is stored for @code{USERNAME} on @code{HOST} and cannot be
used by another user and/or on another instance.

There is one potential problem though; for any given @code{(PACKAGE
  . LOCAL-MACHINE)} there can only be one token identified by "Emacs
package PACKAGE @@ LOCAL-MACHINE"; Github does not allow multiple
tokens with the same description because it uses the description as
the identifier (it could use some hash instead, but alas it does
not).

If you have multiple machines and some of them have the same name,
then you should probably change that as this is not how things ought
to be.  However if you dual-boot, then it might make sense to give
that machine the same name regardless of what operating system you
have booted into.

You could use the same token on both operating systems, but setting
that up might be somewhat difficult because it is not possible to
download an existing token from Github.  You could, of course,
locally copy the token, but that is inconvenient and would make it
harder to only revoke the token used on your infected Windows
installation without also revoking it for your totally safe *BSD
installation.

Alternatively you can set this variable to a unique value, that will
then be used to identify the local machine instead of the value
returned by @code{system-name}.
@end defvar

@node GraphQL Support
@chapter GraphQL Support

@defun ghub-graphql graphql &optional variables &key username auth host callback silent callback errorback value extra

This function makes a GraphQL request using @code{GRAPHQL} and
@code{VARIABLES} as inputs.  @code{GRAPHQL} is a GraphQL string.  @code{VARIABLES}
is a JSON-like alist.  The other arguments behave as for
@code{ghub-request} (which see).

The response is returned as a JSON-like alist.  Even if the response
contains @code{errors}, this function does not raise an error.
Cursor-handling is likewise left to the caller.
@end defun

@code{ghub-graphql} is a thin convenience wrapper around @code{ghub-request},
similar to @code{ghub-post} and friends.  While the latter only hard-code
the value of the @code{METHOD} argument, the former also hard-codes @code{RESOURCE}
and constructs @code{PAYLOAD} from @code{GRAPHEQL} and @code{VARIABLES}.  It also drops
@code{UNPAGINATE}, @code{NOERROR}, @code{READER} (internal functions expect alist-ified
JSON) and @code{FORGE} (only Github currently supports GraphQL).

@code{ghub-graphql} does not account for the fact that pagination works
differently in GraphQL than it does in REST, so users of this function
have to deal with that themselves.  Likewise error handling works
differently and has to be done by the caller too.

An early attempt at implementing automatic unpaginating for GraphQL
can be found in the @code{faithful-graphql} branch, provided I haven't
deleted that by now.  On that branch I try to do things as intended by
the designers of GraphQL, using variables and fragments, and drowning
in a sea of boilerplate.

The problem with that approach is that it only works for applications
that fetch specific information on demand and actually want things to
be paginated.  I am convinced that GraphQL is very nice for web apps.

However the Forge package for which I am implementing all of this has
very different needs.  It wants to fetch "all the data" and "cache"
it locally, so that it is available even when there is no internet
connection.  GraphQL was designed around the idea that you should be
able to "ask for what you need and get exactly that".  But when that
boils down to "look, if I persist, then you are going to hand me over
all the data anyway, so just caught it up already", then things start
to fall apart.  If Github's GraphQL allowed pagination to be turned
off completely, then teaching @code{ghub-graphql} about error handling would
be enough.

But it doesn't and when doing things as intended, then that leads to
huge amounts of repetitive boilerplate, which is so boring to write
that doing it without introducing bugs left and right is near
impossible; so I decided to give up on GraphQL variables, fragments
and conditions, and instead implement something more powerful, though
also more opinionated.

@defun ghub--graphql-vacuum query variables callback &optional until &key narrow username auth host forge

This function is an opinionated alternative to @code{ghub-graphql}.
It relies and dark magic to get the job done.

It makes an initial request using @code{QUERY}.  It then looks for
paginated edges in the returned data and makes more requests to
resolve them.  In order to do so it automatically transforms the
initial @code{QUERY} into another query suitable for that particular edge.
The data retrieved by subsequent requests is then injected into the
data of the original request before that is returned or passed to
the callback.  If subsequently retrieved data features new paginated
edges, then those are followed recursively.

The end result is essentially the same as using @code{ghub-graphql}, if
only it were possible to say "do not paginate anything".  The
implementation is much more complicated because it is not possible
to do that.

@code{QUERY} is a GraphQL query expressed as an s-expression.  The @code{graphql}
package is used to turn that into a GraphQL query string, but the
format is somewhat different than as documented for that package.
Also only a subset of the GraphQL features are supported; fragments
for example are not, and magical stuff happens to variables.  This
is not documented yet, I am afraid.  Look at existing callers.

@code{VARIABLES} is a JSON-like alist as for @code{ghub-graphql}.

@code{UNTIL} is an alist @code{((EDGE-until . VALUE)...)}.  When unpaginating @code{EDGE}
try not to fetch beyond the element whose first field has the value
@code{VALUE} and remove that element as well as all "lesser" elements from
the retrieved data if necessary.  Look at @code{forge--pull-repository} for
an example.  This is only useful if you "cache" the response locally
and want to avoid fetching data again that you already have.

Other arguments behave as for @code{ghub-graphql} and @code{ghub-request}, more or
less.
@end defun

Using @code{ghub--graphql-vacuum}, the following resource specific functions
are implemented.  These functions are not part of the public API yet
and are very much subject to change.

@defun ghub-fetch-repository owner name callback &optional until &key username auth host forge

This function asynchronously fetches forge data about the specified
repository.  Once all data has been collected, @code{CALLBACK} is called
with the data as the only argument.
@end defun

@defun ghub-fetch-issue owner name callback &optional until &key username auth host forge

This function asynchronously fetches forge data about the specified
issue.  Once all data has been collected, @code{CALLBACK} is called
with the data as the only argument.
@end defun

@defun ghub-fetch-pullreq owner name callback &optional until &key username auth host forge

This function asynchronously fetches forge data about the specified
pull-request.  Once all data has been collected, @code{CALLBACK} is called
with the data as the only argument.
@end defun

Note that in order to avoid duplication all of these functions base
their initial query on the query stored in @code{ghub-fetch-repository}.  The
latter two pass that query through @code{ghub--graphql-prepare-query}, which
then used @code{ghub--graphql-narrow-query} to remove parts the caller is not
interested in.  These two functions are also used internally, when
unpaginating, but as demonstrated here they can be useful even before
making an initial request.

@node Support for Other Forges
@chapter Support for Other Forges

@menu
* Forge Functions and Variables::
* Forge Limitations and Notes::
@end menu

@node Forge Functions and Variables
@section Forge Functions and Variables

Originally Ghub supported only Github but now it also supports Gitlab,
Gitea, Gogs and Bitbucket.  The function @code{ghub-request} and all the
@code{ghub-METHOD} convenience wrappers default to acting on a Github forge
but can be told to act on another forge using their FORGE argument.

The FORGE argument only specifies what kind of forge to act on, not
which instance.  The HOST argument can be used to select the instance.
For some forges a default instance is defined:

@itemize
@item
Forge @code{github} defaults to host @code{api.github.com}.

@item
Forge @code{gitlab} defaults to host @code{gitlab.com/api/v4}.

@item
Forge @code{bitbucket} defaults to host @code{api.bitbucket.org/2.0}.

@item
No canonical host exists for the @code{gitea} and @code{gogs} forges and
@code{localhost:3000/api/v1} is used as the default host in both cases.
@end itemize

Together the FORGE and HOST arguments specify the forge type and
instance.  In addition to that, it is also necessary to specify on
whose behalf the request is being made, which can be done using the
USERNAME and AUTH arguments.

Having to specify these arguments for every request is inconvenient.
Additional variables and convenience functions can be used to make
that unnecessary in most cases.

These variables can be set globally and/or for a specific repository
as explained in @ref{Configuration Variables} with a focus on Github
instances.  To summarize:

@itemize
@item
For @uref{https://github.com} the Git variable @code{github.user} specifies the
user.

@item
For another @code{github} instance the Git variable @code{github.HOST.user}
specifies the user.  The HOST in that variable name is the same
as the value of the HOST argument of the called function.

@item
Instead of specifying the HOST in every function call, the Git
variable @code{github.host} can be used.  This should only be set locally.
@end itemize

@noindent
For @code{gitlab} and @code{bitbucket} forges similar variables are available:

@itemize
@item
@code{gitlab.user} specifies the @uref{https://gitlab.com} user.

@item
@code{gitlab.HOST.user} specifies the user for the HOST @code{gitlab} instance.

@item
@code{gitlab.host} specifies the @code{gitlab} host, unless the HOST argument
is non-nil

@item
@code{bitbucket.user} specifies the @uref{https://bitbucket.org} user.

@item
@code{bitbucket.HOST.user} specifies the user for the HOST @code{bitbucket}
instance.

@item
@code{bitbucket.host} specifies the @code{bitbucket} host, unless the HOST
argument is non-nil.
@end itemize

For @code{gitea} and @code{gogs} forges some similar variables are available,
however for some of the @code{ghub.*} variables no equivalent variable
exist for these two forges:

@itemize
@item
@code{gitea.user} is @strong{not} used because no canonical @code{gitea} instance exists.

@item
@code{gitea.HOST.user} specifies the user for the HOST @code{gitea} instance.

@item
@code{gitea.host} specifies the @code{gitea} host, unless the HOST argument is
non-nil

@item
@code{gogs.user} is @strong{not} used because no canonical @code{gitea} instance exists.

@item
@code{gogs.HOST.user} specifies the user for the HOST @code{gogs} instance.

@item
@code{gogs.host} specifies the @code{gogs} host, unless the HOST argument is
non-nil
@end itemize

@code{ghub-request} and @code{ghub-METHOD} can be used to make a request for any
of the supported forge types, but except when making a request for
a @code{github} instance, then that requires the use of the FORGE argument.

To avoid that, functions named @code{FORGE-request} and @code{FORGE-METHOD} are also
available.  The following forms are equivalent, for example:

@lisp
(ghub-get ... :auth 'PACKAGE :forge 'gitlab)
(glab-get ... :auth 'PACKAGE)
@end lisp

These forms would remain equivalent even if you did not specify a
value for the AUTH arguments — but you should not do that if you plan
to share your code with others (see @ref{Using Ghub in a Package}).  If you
do omit AUTH, then the request is made on behalf of the @code{ghub} package,
@strong{regardless} of the symbol prefix of the function you use to do so.

All @code{FORGE-request} and @code{FORGE-METHOD} functions, including but not
limited to @code{ghub-METHOD}, are very simple wrappers around @code{ghub-request}.
They take fewer arguments than @code{ghub-request} and instead pass constant
values for the arguments METHOD and/or FORGE@.

@node Forge Limitations and Notes
@section Forge Limitations and Notes

@itemize
@item
The token creation wizard is only available for @code{github} forges,
because all other forges do not support using the API to create an
API token.  As a consequence, if the user makes a request and the
necessary token cannot be found, then that results in an error.
Tokens can be created at:

@itemize
@item
Gitlab: @uref{https://gitlab.com/profile/personal_access_tokens}

@item
Bitbucket: @uref{https://bitbucket.org/account/user/tarsius/app-passwords}

@item
Gitea: @uref{https://localhost:3000/user/settings/applications}

@item
Gogs: @uref{https://localhost:3000/user/settings/applications}
@end itemize

Also see @ref{Manually Creating and Storing a Token} and @ref{How Ghub uses Auth-Source}.


@item
As mentioned in the previous node, the variables @code{gitea.host} and
@code{gogs.host} are not taken into account.


@item
Gitea and Gogs do not support limiting a token to certain scopes.


@item
The Bitbucket API is fairly broken.  Some resources only work if a
slash is appended while others only work if no slash is appended.  I
am unable to access any private repositories and some resources
don't work for me at all.  Also the API is only RESTish; pagination
information is part of the response body instead of the header.  Due
to such issues it is possible that I will eventually have to remove
support for Bitbucket altogether.


@item
The Gitlab API documentation is not always accurate, though I don't
have an example at hand.  It also isn't structured well, making it
occationally difficult to find the information one is looking for.


@item
Where one would use @code{user/repo} when accessing another forge, one has
to use @code{user%2Frepo} when accessing Gitlab, e.g.:

@lisp
(glab-get "/projects/python-mode-devs%2Fpython-mode")
@end lisp
@end itemize

@bye
