commit: pass author/committer info to hooks

When lying the author name via GIT_AUTHOR_NAME environment variable
to "git commit", the hooks run by the command saw it and could act
on the name that will be recorded in the final commit. When the user
uses the "--author" option from the command line, the command should
give the same information to the hook, and back when "git command"
was a scripted Porcelain, it did set the environment variable and
hooks can learn the author name from it.

However, when the command was reimplemented in C, the rewritten code
was not very faithful to the original, and hooks stopped getting the
authorship information given with "--author".  Fix this by exporting
the necessary environment variables.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/commit.c

@@ -533,9 +533,20 @@ static int is_a_merge(const struct commit *current_head)
 
 static const char sign_off_header[] = "Signed-off-by: ";
 
+static void export_one(const char *var, const char *s, const char *e, int hack)
+{
+	struct strbuf buf = STRBUF_INIT;
+	if (hack)
+		strbuf_addch(&buf, hack);
+	strbuf_addf(&buf, "%.*s", (int)(e - s), s);
+	setenv(var, buf.buf, 1);
+	strbuf_release(&buf);
+}
+
 static void determine_author_info(struct strbuf *author_ident)
 {
 	char *name, *email, *date;
+	struct ident_split author;
 
 	name = getenv("GIT_AUTHOR_NAME");
 	email = getenv("GIT_AUTHOR_EMAIL");
@@ -585,6 +596,11 @@ static void determine_author_info(struct strbuf *author_ident)
 		date = force_date;
 	strbuf_addstr(author_ident, fmt_ident(name, email, date,
 					      IDENT_ERROR_ON_NO_NAME));
+	if (!split_ident_line(&author, author_ident->buf, author_ident->len)) {
+		export_one("GIT_AUTHOR_NAME", author.name_begin, author.name_end, 0);
+		export_one("GIT_AUTHOR_EMAIL", author.mail_begin, author.mail_end, 0);
+		export_one("GIT_AUTHOR_DATE", author.date_begin, author.tz_end, '@');
+	}
 }
 
 static int ends_rfc2822_footer(struct strbuf *sb)
@@ -652,6 +668,9 @@ static int prepare_to_commit(const char *index_file, const char *prefix,
 	int ident_shown = 0;
 	int clean_message_contents = (cleanup_mode != CLEANUP_NONE);
 
+	/* This checks and barfs if author is badly specified */
+	determine_author_info(author_ident);
+
 	if (!no_verify && run_hook(index_file, "pre-commit", NULL))
 		return 0;
 
@@ -771,9 +790,6 @@ static int prepare_to_commit(const char *index_file, const char *prefix,
 
 	strbuf_release(&sb);
 
-	/* This checks and barfs if author is badly specified */
-	determine_author_info(author_ident);
-
 	/* This checks if committer ident is explicitly given */
 	strbuf_addstr(&committer_ident, git_committer_info(0));
 	if (use_editor && include_status) {

t/t7503-pre-commit-hook.sh

@@ -118,7 +118,7 @@ test_expect_success 'with failing hook requiring GIT_PREFIX' '
 	git checkout -- file
 '
 
-test_expect_failure 'check the author in hook' '
+test_expect_success 'check the author in hook' '
 	write_script "$HOOK" <<-\EOF &&
 	test "$GIT_AUTHOR_NAME" = "New Author" &&
 	test "$GIT_AUTHOR_EMAIL" = "newauthor@example.com"