pretty: make empty userformats truly empty

If the user provides an empty format with "--format=", we
end up putting in extra whitespace that the user cannot
prevent. This comes from two places:

  1. If the format is missing a terminating newline, we add
     one automatically. This makes sense for --format=%h, but
     not for a truly empty format.

  2. We add an extra newline between the pretty-printed
     format and a diff or diffstat. If the format is empty,
     there's no point in doing so if there's nothing to
     separate.

With this patch, one can get a diff with no other cruft out
of "diff-tree --format= $commit".

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

1 files changed, 1 insertions, 0 deletions

diff --git a/commit.h b/commit.h
index a8cbf52..aa8c3ca 100644
--- a/commit.h
+++ b/commit.h
@@ -159,6 +159,7 @@ extern void get_commit_format(const char *arg, struct rev_info *);
 extern const char *format_subject(struct strbuf *sb, const char *msg,
 				  const char *line_separator);
 extern void userformat_find_requirements(const char *fmt, struct userformat_want *w);
+extern int commit_format_is_empty(enum cmit_fmt);
 extern void format_commit_message(const struct commit *commit,
 				  const char *format, struct strbuf *sb,
 				  const struct pretty_print_context *context);