Merge branch 'bc/doc-credential-helper-value'

Doc update.

* bc/doc-credential-helper-value:
  docs: document credential.helper allowed values

Author: gitster

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