[PATCH] Documentation/git-am: Document supported --patch-format options

The --patch-format option has been supported for a while but it is not
mentioned in the man page and the short help cannot tell the user what
the supported formats are. Add the option to the man page along with the
supported options.

Signed-off-by: Chris Packham <redacted>
---
I've not bothered to actually explain what the options mean. I'm not
sure if readers will care aside from just trying them until one works
(that's all I did when I had a patch that failed detection).

 Documentation/git-am.txt |   12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/Documentation/git-am.txt b/Documentation/git-am.txt
index 54d8461..76bd359 100644
--- a/Documentation/git-am.txt
+++ b/Documentation/git-am.txt

@@ -12,9 +12,9 @@ SYNOPSIS
 'git am' [--signoff] [--keep] [--[no-]keep-cr] [--[no-]utf8]
 	 [--3way] [--interactive] [--committer-date-is-author-date]
 	 [--ignore-date] [--ignore-space-change | --ignore-whitespace]
-	 [--whitespace=<option>] [-C<n>] [-p<n>] [--directory=<dir>]
-	 [--exclude=<path>] [--include=<path>] [--reject] [-q | --quiet]
-	 [--[no-]scissors]
+	 [--whitespace=<option>] [-C<n>] [-p<n>] [--patch-format=<format>]
+	 [--directory=<dir>] [--exclude=<path>] [--include=<path>]
+	 [--reject] [-q | --quiet] [--[no-]scissors]
 	 [(<mbox> | <Maildir>)...]
 'git am' (--continue | --skip | --abort)
 

@@ -97,6 +97,12 @@ default.   You can use `--no-utf8` to override this.
 	program that applies
 	the patch.
 
+--patch-format::
+	By default the command will try to detect the patch format
+	automatically. This option allows the user to bypass the automatic
+	detection and specify the patch format that the patch(es) should be
+	intepreted as. Valid formats are mbox, stgit, stgit-series and hg.
+
 -i::
 --interactive::
 	Run interactively.