path: root/Documentation/gitcredentials.txt
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Diffstat (limited to 'Documentation/gitcredentials.txt')
1 files changed, 88 insertions, 1 deletions
diff --git a/Documentation/gitcredentials.txt b/Documentation/gitcredentials.txt
index ea759fd..5b9d14f 100644
--- a/Documentation/gitcredentials.txt
+++ b/Documentation/gitcredentials.txt
@@ -186,7 +186,94 @@ CUSTOM HELPERS
You can write your own custom helpers to interface with any system in
-which you keep credentials. See credential.h for details.
+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"
+# 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:
+ Return a matching credential, if any exists.
+ Store the credential, if applicable to the helper.
+ 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
+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).