doc: move credential helper info into gitcredentials(7)

[thirdparty/git.git] / Documentation / gitcredentials.txt

gitcredentials(7)
=================

NAME
----
gitcredentials - providing usernames and passwords to Git

SYNOPSIS
--------
------------------
git config credential.https://example.com.username myusername
git config credential.helper "$helper $options"
------------------

DESCRIPTION
-----------

Git will sometimes need credentials from the user in order to perform
operations; for example, it may need to ask for a username and password
in order to access a remote repository over HTTP. This manual describes
the mechanisms Git uses to request these credentials, as well as some
features to avoid inputting these credentials repeatedly.

REQUESTING CREDENTIALS
----------------------

Without any credential helpers defined, Git will try the following
strategies to ask the user for usernames and passwords:

1. If the `GIT_ASKPASS` environment variable is set, the program
   specified by the variable is invoked. A suitable prompt is provided
   to the program on the command line, and the user's input is read
   from its standard output.

2. Otherwise, if the `core.askPass` configuration variable is set, its
   value is used as above.

3. Otherwise, if the `SSH_ASKPASS` environment variable is set, its
   value is used as above.

4. Otherwise, the user is prompted on the terminal.

AVOIDING REPETITION
-------------------

It can be cumbersome to input the same credentials over and over.  Git
provides two methods to reduce this annoyance:

1. Static configuration of usernames for a given authentication context.

2. Credential helpers to cache or store passwords, or to interact with
   a system password wallet or keychain.

The first is simple and appropriate if you do not have secure storage available
for a password. It is generally configured by adding this to your config:

---------------------------------------
[credential "https://example.com"]
	username = me
---------------------------------------

Credential helpers, on the other hand, are external programs from which Git can
request both usernames and passwords; they typically interface with secure
storage provided by the OS or other programs.

To use a helper, you must first select one to use. Git currently
includes the following helpers:

cache::

	Cache credentials in memory for a short period of time. See
	linkgit:git-credential-cache[1] for details.

store::

	Store credentials indefinitely on disk. See
	linkgit:git-credential-store[1] for details.

You may also have third-party helpers installed; search for
`credential-*` in the output of `git help -a`, and consult the
documentation of individual helpers.  Once you have selected a helper,
you can tell Git to use it by putting its name into the
credential.helper variable.

1. Find a helper.
+
-------------------------------------------
$ git help -a | grep credential-
credential-foo
-------------------------------------------

2. Read its description.
+
-------------------------------------------
$ git help credential-foo
-------------------------------------------

3. Tell Git to use it.
+
-------------------------------------------
$ git config --global credential.helper foo
-------------------------------------------


CREDENTIAL CONTEXTS
-------------------

Git considers each credential to have a context defined by a URL. This context
is used to look up context-specific configuration, and is passed to any
helpers, which may use it as an index into secure storage.

For instance, imagine we are accessing `https://example.com/foo.git`. When Git
looks into a config file to see if a section matches this context, it will
consider the two a match if the context is a more-specific subset of the
pattern in the config file. For example, if you have this in your config file:

--------------------------------------
[credential "https://example.com"]
	username = foo
--------------------------------------

then we will match: both protocols are the same, both hosts are the same, and
the "pattern" URL does not care about the path component at all. However, this
context would not match:

--------------------------------------
[credential "https://kernel.org"]
	username = foo
--------------------------------------

because the hostnames differ. Nor would it match `foo.example.com`; Git
compares hostnames exactly, without considering whether two hosts are part of
the same domain. Likewise, a config entry for `http://example.com` would not
match: Git compares the protocols exactly.

If the "pattern" URL does include a path component, then this too must match
exactly: the context `https://example.com/bar/baz.git` will match a config
entry for `https://example.com/bar/baz.git` (in addition to matching the config
entry for `https://example.com`) but will not match a config entry for
`https://example.com/bar`.


CONFIGURATION OPTIONS
---------------------

Options for a credential context can be configured either in
`credential.*` (which applies to all credentials), or
`credential.<url>.*`, where <url> matches the context as described
above.

The following options are available in either location:

helper::

	The name of an external credential helper, and any associated options.
	If the helper name is not an absolute path, then the string `git
	credential-` is prepended. The resulting string is executed by the
	shell (so, for example, setting this to `foo --option=bar` will execute
	`git credential-foo --option=bar` via the shell. See the manual of
	specific helpers for examples of their use.
+
If there are multiple instances of the `credential.helper` configuration
variable, each helper will be tried in turn, and may provide a username,
password, or nothing. Once Git has acquired both a username and a
password, no more helpers will be tried.
+
If `credential.helper` is configured to the empty string, this resets
the helper list to empty (so you may override a helper set by a
lower-priority config file by configuring the empty-string helper,
followed by whatever set of helpers you would like).

username::

	A default username, if one is not provided in the URL.

useHttpPath::

	By default, Git does not consider the "path" component of an http URL
	to be worth matching via external helpers. This means that a credential
	stored for `https://example.com/foo.git` will also be used for
	`https://example.com/bar.git`. If you do want to distinguish these
	cases, set this option to `true`.


CUSTOM HELPERS
--------------

You can write your own custom helpers to interface with any system in
which you keep credentials.

Credential helpers are programs executed by Git to fetch or save
credentials from and to long-term storage (where "long-term" is simply
longer than a single Git process; e.g., credentials may be stored
in-memory for a few minutes, or indefinitely on disk).

Each helper is specified by a single string in the configuration
variable `credential.helper` (and others, see linkgit:git-config[1]).
The string is transformed by Git into a command to be executed using
these rules:

  1. If the helper string begins with "!", it is considered a shell
     snippet, and everything after the "!" becomes the command.

  2. Otherwise, if the helper string begins with an absolute path, the
     verbatim helper string becomes the command.

  3. Otherwise, the string "git credential-" is prepended to the helper
     string, and the result becomes the command.

The resulting command then has an "operation" argument appended to it
(see below for details), and the result is executed by the shell.

Here are some example specifications:

----------------------------------------------------
# run "git credential-foo"
foo

# same as above, but pass an argument to the helper
foo --bar=baz

# the arguments are parsed by the shell, so use shell
# quoting if necessary
foo --bar="whitespace arg"

# you can also use an absolute path, which will not use the git wrapper
/path/to/my/helper --with-arguments

# or you can specify your own shell snippet
!f() { echo "password=`cat $HOME/.secret`"; }; f
----------------------------------------------------

Generally speaking, rule (3) above is the simplest for users to specify.
Authors of credential helpers should make an effort to assist their
users by naming their program "git-credential-$NAME", and putting it in
the `$PATH` or `$GIT_EXEC_PATH` during installation, which will allow a
user to enable it with `git config credential.helper $NAME`.

When a helper is executed, it will have one "operation" argument
appended to its command line, which is one of:

`get`::

	Return a matching credential, if any exists.

`store`::

	Store the credential, if applicable to the helper.

`erase`::

	Remove a matching credential, if any, from the helper's storage.

The details of the credential will be provided on the helper's stdin
stream. The exact format is the same as the input/output format of the
`git credential` plumbing command (see the section `INPUT/OUTPUT
FORMAT` in linkgit:git-credential[1] for a detailed specification).

For a `get` operation, the helper should produce a list of attributes on
stdout in the same format (see linkgit:git-credential[1] for common
attributes). A helper is free to produce a subset, or even no values at
all if it has nothing useful to provide. Any provided attributes will
overwrite those already known about by Git.  If a helper outputs a
`quit` attribute with a value of `true` or `1`, no further helpers will
be consulted, nor will the user be prompted (if no credential has been
provided, the operation will then fail).

For a `store` or `erase` operation, the helper's output is ignored.
If it fails to perform the requested operation, it may complain to
stderr to inform the user. If it does not support the requested
operation (e.g., a read-only store), it should silently ignore the
request.

If a helper receives any other operation, it should silently ignore the
request. This leaves room for future operations to be added (older
helpers will just ignore the new requests).

GIT
---
Part of the linkgit:git[1] suite