pretty: add support for separator option in %(trailers)

By default trailer lines are terminated by linebreaks ('\n'). By
specifying the new 'separator' option they will instead be separated by
user provided string and have separator semantics rather than terminator
semantics. The separator string can contain the literal formatting codes
%n and %xNN allowing it to be things that are otherwise hard to type
such as %x00, or comma and end-parenthesis which would break parsing.

E.g:
 $ git log --pretty='%(trailers:key=Reviewed-by,valueonly,separator=%x00)'

Signed-off-by: Anders Waldenborg <anders@0x63.nu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 9 insertions, 0 deletions

diff --git a/Documentation/pretty-formats.txt b/Documentation/pretty-formats.txt
index 76e2dbdb71..4cfea4c9d6 100644
--- a/Documentation/pretty-formats.txt
+++ b/Documentation/pretty-formats.txt
@@ -239,6 +239,15 @@ endif::git-rev-list[]
    `false`, `off`, `no` to show the non-trailer lines. If option is
    given without value it is enabled. If given multiple times the last
    value is used.
+** 'separator=<SEP>': specify a separator inserted between trailer
+   lines. When this option is not given each trailer line is
+   terminated with a line feed character. The string SEP may contain
+   the literal formatting codes described above. To use comma as
+   separator one must use `%x2C` as it would otherwise be parsed as
+   next option. If separator option is given multiple times only the
+   last one is used. E.g., `%(trailers:key=Ticket,separator=%x2C )`
+   shows all trailer lines whose key is "Ticket" separated by a comma
+   and a space.
 ** 'unfold[=val]': make it behave as if interpret-trailer's `--unfold`
    option was given. In same way as to for `only` it can be followed
    by an equal sign and explicit value. E.g.,