pretty: support normalization options for %(trailers)

The interpret-trailers command recently learned some options
to make its output easier to parse (for a caller whose only
interested in picking out the trailer values). But it's not
very efficient for asking for the trailers of many commits
in a single invocation.

We already have "%(trailers)" to do that, but it doesn't
know about unfolding or omitting non-trailers. Let's plumb
those options through, so you can have the best of both.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 4 insertions, 1 deletions

diff --git a/Documentation/pretty-formats.txt b/Documentation/pretty-formats.txt
index 4d6dac5770..efa67a716e 100644
--- a/Documentation/pretty-formats.txt
+++ b/Documentation/pretty-formats.txt
@@ -201,7 +201,10 @@ endif::git-rev-list[]
 - '%><(<N>)', '%><|(<N>)': similar to '% <(<N>)', '%<|(<N>)'
   respectively, but padding both sides (i.e. the text is centered)
 - %(trailers): display the trailers of the body as interpreted by
-  linkgit:git-interpret-trailers[1]
+  linkgit:git-interpret-trailers[1]. If the `:only` option is given,
+  omit non-trailer lines from the trailer block.  If the `:unfold`
+  option is given, behave as if interpret-trailer's `--unfold` option
+  was given. E.g., `%(trailers:only:unfold)` to do both.
 
 NOTE: Some placeholders may depend on other options given to the
 revision traversal engine. For example, the `%g*` reflog options will