format-patch: fix From header in cover letter

"git format-patch" takes "--from=<user ident>" command line option
and uses the given ident for patch e-mails, but this is not applied
to the cover letter, the option is ignored and the committer ident
of the current user is used. This has been the case ever since
"--from" was introduced in a908047 (teach format-patch to place
other authors into in-body "From", 2013-07-03).

Teach the make_cover_letter() function to honor the option, instead of
always using the current committer identity. Change variable name from
"committer" to "from" to better reflect the purpose of the variable.

Signed-off-by: Mirko Faina <mroik@delayed.space>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: Mroik

Documentation/git-format-patch.adoc

@@ -282,11 +282,12 @@ e.g., `--rfc='-(WIP)'` results in "PATCH (WIP)".
 
 --from::
 --from=<ident>::
-	Use `ident` in the `From:` header of each commit email. If the
-	author ident of the commit is not textually identical to the
-	provided `ident`, place a `From:` header in the body of the
-	message with the original author. If no `ident` is given, use
-	the committer ident.
+	Use `ident` in the `From:` header of each email. In case of a
+	commit email, if the author ident of the commit is not textually
+	identical to the provided `ident`, place a `From:` header in the
+	body of the message with the original author. If no `ident` is
+	given, or if the option is not passed at all, use the ident of
+	the current committer.
 +
 Note that this option is only useful if you are actually sending the
 emails and want to identify yourself as the sender, but retain the

builtin/log.c

@@ -1332,7 +1332,7 @@ static void make_cover_letter(struct rev_info *rev, int use_separate_file,
 			      int quiet,
 			      const struct format_config *cfg)
 {
-	const char *committer;
+	const char *from;
 	struct shortlog log;
 	struct strbuf sb = STRBUF_INIT;
 	int i;
@@ -1345,7 +1345,7 @@ static void make_cover_letter(struct rev_info *rev, int use_separate_file,
 	if (!cmit_fmt_is_mail(rev->commit_format))
 		die(_("cover letter needs email format"));
 
-	committer = git_committer_info(0);
+	from = cfg->from ? cfg->from : git_committer_info(0);
 
 	if (use_separate_file &&
 	    open_next_file(NULL, rev->numbered_files ? NULL : "cover-letter", rev, quiet))
@@ -1368,7 +1368,7 @@ static void make_cover_letter(struct rev_info *rev, int use_separate_file,
 	pp.date_mode.type = DATE_RFC2822;
 	pp.rev = rev;
 	pp.encode_email_headers = rev->encode_email_headers;
-	pp_user_info(&pp, NULL, &sb, committer, encoding);
+	pp_user_info(&pp, NULL, &sb, from, encoding);
 	prepare_cover_text(&pp, description_file, branch_name, &sb,
 			   encoding, need_8bit_cte, cfg);
 	fprintf(rev->diffopt.file, "%s\n", sb.buf);

t/t4014-format-patch.sh

@@ -1472,6 +1472,14 @@ test_expect_success '--from uses committer ident' '
 	test_cmp expect patch.head
 '
 
+test_expect_success '--from applies to cover letter' '
+	test_when_finished "rm -rf patches" &&
+	git format-patch -1 --cover-letter --from="Foo Bar <author@example.com>" -o patches &&
+	echo "From: Foo Bar <author@example.com>" >expect &&
+	grep "^From:" patches/0000-cover-letter.patch >patch.head &&
+	test_cmp expect patch.head
+'
+
 test_expect_success '--from omits redundant in-body header' '
 	git format-patch -1 --stdout --from="A U Thor <author@example.com>" >patch &&
 	cat >expect <<-\EOF &&