format-patch: refactor get_patch_filename

The get_patch_filename function expects a commit argument
and uses it to get the sanitized subject line when making a
patch filename. However, we also want to use this same
function for the cover letter, which does not have a commit
object. The current solution is to create a fake commit with
the subject "cover letter". Instead, let's make the
get_patch_filename interface more flexibile, and allow
passing a direct subject.

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

1 files changed, 2 insertions, 2 deletions

diff --git a/log-tree.h b/log-tree.h
index 5c4cf7c..f5ac238 100644
--- a/log-tree.h
+++ b/log-tree.h
@@ -21,7 +21,7 @@ void log_write_email_headers(struct rev_info *opt, struct commit *commit,
 void load_ref_decorations(int flags);
 
 #define FORMAT_PATCH_NAME_MAX 64
-void get_patch_filename(struct commit *commit, int nr, const char *suffix,
-			struct strbuf *buf);
+void get_patch_filename(struct commit *commit, const char *subject, int nr,
+			const char *suffix, struct strbuf *buf);
 
 #endif