Re: A possible fmt-merge-msg update?

[Junio C Hamano <gitster@pobox.com>]

Linus Torvalds <torvalds@linux-foundation.org> writes:

> On Sun, Mar 4, 2012 at 7:17 PM, Junio C Hamano <gitster@pobox.com> wrote:
>>
>> Having observed a handful of your recent merge messages, I am wondering if
>> it would help to teach fmt-merge-msg to include "from Wim Van Sebroeck" in
>> its output by taking the committer of the MERGE_HEAD into account.
>>
>> Not worth the trouble?
>
> Hmm. Maybe worth it.
> ...
> It might be interesting if the pre-written commit message had the top
> committer in a comment (the same way pulling a tag has the tag author
> in the comment about the tag verification). That way the information
> would be right there when I edit the message, and since it's correct
> 99% of the time it would make it easier to just edit it in the editor
> than have to cut-and-paste it from the email. But because it's not a
> sure thing,...

The attached would give me:

| Merge branch 'jl/maint-submodule-relative'
| 
| # Jens Lehmann (3) and Johannes Sixt (1)
| * jl/maint-submodule-relative:
|   submodules: fix ambiguous absolute paths under Windows
|   submodules: refactor computation of relative gitdir path
|   submodules: always use a relative path from gitdir to work tree
|   submodules: always use a relative path to gitdir

It would be a sure thing for the commit-authorship, so we could use
"By " instead of "# " above, but it should be obvious either way.

The existing test vectors need to be taught about this change if we
were to do something like this.

-- >8 --
Subject: [PATCH] fmt-merge-msg: show primary authors of a merged series

As we already walk the history of the branch that gets merged to
come up with a short log, let's label it with names of the primary
authors, so that the user who summarizes the merge can easily give
credit to them in the log message.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 builtin/fmt-merge-msg.c |   61 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 61 insertions(+)

diff --git a/builtin/fmt-merge-msg.c b/builtin/fmt-merge-msg.c
index c81a7fe..7eea066 100644
--- a/builtin/fmt-merge-msg.c
+++ b/builtin/fmt-merge-msg.c
@@ -180,6 +180,63 @@ static void add_branch_desc(struct strbuf *out, const char *name)
 	strbuf_release(&desc);
 }
 
+static void record_author(struct string_list *authors, struct commit *commit)
+{
+	char name_buf[MAX_GITNAME], *name, *name_end;
+	struct string_list_item *elem;
+
+	name = strstr(commit->buffer, "\nauthor ");
+	if (!name)
+		return;
+	name += strlen("\nauthor ");
+	name_end = strchrnul(name, '<');
+	if (*name_end)
+		name_end--;
+	while (isspace(*name_end) && name <= name_end)
+		name_end--;
+	if (name_end < name || name + MAX_GITNAME <= name_end)
+		return;
+	memcpy(name_buf, name, name_end - name + 1);
+	name_buf[name_end - name + 1] = '\0';
+
+	elem = string_list_lookup(authors, name_buf);
+	if (!elem) {
+		elem = string_list_insert(authors, name_buf);
+		elem->util = (void *) 0;
+	}
+	elem->util = (void*)(((intptr_t)elem->util) + 1);
+}
+
+#define util_as_int(elem) ((intptr_t)((elem)->util))
+
+static int cmp_string_list_util_as_int(const void *a_, const void *b_)
+{
+	const struct string_list_item *a = a_, *b = b_;
+	return util_as_int(b) - util_as_int(a);
+}
+
+static void add_author_info(struct strbuf *out, struct string_list *authors)
+{
+	if (!authors->nr)
+		return;
+	qsort(authors->items, authors->nr, sizeof(authors->items[0]),
+	      cmp_string_list_util_as_int);
+
+	strbuf_addstr(out, "\n# ");
+	if (authors->nr == 1)
+		strbuf_addf(out, "%s", authors->items[0].string);
+	else if (authors->nr == 2)
+		strbuf_addf(out, "%s (%d) and %s (%d)",
+			    authors->items[0].string,
+			    (int)util_as_int(&authors->items[0]),
+			    authors->items[1].string,
+			    (int)util_as_int(&authors->items[1]));
+	else
+		strbuf_addf(out, "%s (%d) and others",
+			    authors->items[0].string,
+			    (int)util_as_int(&authors->items[0]));
+}
+
 static void shortlog(const char *name,
 		     struct origin_data *origin_data,
 		     struct commit *head,
@@ -190,6 +247,7 @@ static void shortlog(const char *name,
 	struct commit *commit;
 	struct object *branch;
 	struct string_list subjects = STRING_LIST_INIT_DUP;
+	struct string_list authors = STRING_LIST_INIT_DUP;
 	int flags = UNINTERESTING | TREESAME | SEEN | SHOWN | ADDED;
 	struct strbuf sb = STRBUF_INIT;
 	const unsigned char *sha1 = origin_data->sha1;
@@ -212,6 +270,7 @@ static void shortlog(const char *name,
 		if (commit->parents && commit->parents->next)
 			continue;
 
+		record_author(&authors, commit);
 		count++;
 		if (subjects.nr > limit)
 			continue;
@@ -226,6 +285,7 @@ static void shortlog(const char *name,
 			string_list_append(&subjects, strbuf_detach(&sb, NULL));
 	}
 
+	add_author_info(out, &authors);
 	if (count > limit)
 		strbuf_addf(out, "\n* %s: (%d commits)\n", name, count);
 	else
@@ -246,6 +306,7 @@ static void shortlog(const char *name,
 	rev->commits = NULL;
 	rev->pending.nr = 0;
 
+	string_list_clear(&authors, 0);
 	string_list_clear(&subjects, 0);
 }
 
-- 
1.7.9.2.413.ge58a8e