docs: document credential.helper allowed values

gitcredentials(7) already mentions several possible invocations that one
can use as the value for credential.helper.  However, many people are
not aware that there are other options than a simple credential helper
name, so let's place some explanatory text in the documentation for
credential.helper as well.

We still refer the user to gitcredential(7) for additional explanations
and helpful examples.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Acked-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/Documentation/config/credential.txt b/Documentation/config/credential.txt
index 60fb3189e16144a277cab1c80222c556ce939ed5..9d01641c282aa9cf472dc782e13cd9c430b17e3a 100644 (file)
--- a/Documentation/config/credential.txt
+++ b/Documentation/config/credential.txt
@@ -1,9 +1,13 @@
 credential.helper::
        Specify an external helper to be called when a username or
        password credential is needed; the helper may consult external
-       storage to avoid prompting the user for the credentials. Note
-       that multiple helpers may be defined. See linkgit:gitcredentials[7]
-       for details.
+       storage to avoid prompting the user for the credentials. This is
+       normally the name of a credential helper with possible
+       arguments, but may also be an absolute path with arguments or, if
+       preceded by `!`, shell commands.
++
+Note that multiple helpers may be defined. See linkgit:gitcredentials[7]
+for details and examples.
 
 credential.useHttpPath::
        When acquiring credentials, consider the "path" component of an http