builtin-commit.c: export GIT_INDEX_FILE for launch_editor as well.

The editor program to let the user edit the log message used to
get GIT_INDEX_FILE environment variable pointing at the right
file, but this was lost when git-commit was rewritten in C.

Signed-off-by: Pierre Habouzit <madcoder@debian.org>
Acked-by: Kristian Høgsberg <krh@redhat.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin-commit.c

@@ -748,9 +748,12 @@ int cmd_commit(int argc, const char **argv, const char *prefix)
 
 	/* Get the commit message and validate it */
 	header_len = sb.len;
-	if (!no_edit)
-		launch_editor(git_path(commit_editmsg), &sb);
-	else if (strbuf_read_file(&sb, git_path(commit_editmsg), 0) < 0) {
+	if (!no_edit) {
+		char index[PATH_MAX];
+		const char *env[2] = { index, NULL };
+		snprintf(index, sizeof(index), "GIT_INDEX_FILE=%s", index_file);
+		launch_editor(git_path(commit_editmsg), &sb, env);
+	} else if (strbuf_read_file(&sb, git_path(commit_editmsg), 0) < 0) {
 		rollback_index_files();
 		die("could not read commit message\n");
 	}

builtin-tag.c

@@ -17,7 +17,7 @@ static const char builtin_tag_usage[] =
 
 static char signingkey[1000];
 
-void launch_editor(const char *path, struct strbuf *buffer)
+void launch_editor(const char *path, struct strbuf *buffer, const char *const *env)
 {
 	const char *editor, *terminal;
 
@@ -43,7 +43,7 @@ void launch_editor(const char *path, struct strbuf *buffer)
 	if (strcmp(editor, ":")) {
 		const char *args[] = { editor, path, NULL };
 
-		if (run_command_v_opt(args, 0))
+		if (run_command_v_opt_cd_env(args, 0, NULL, env))
 			die("There was a problem with the editor %s.", editor);
 	}
 
@@ -312,7 +312,7 @@ static void create_tag(const unsigned char *object, const char *tag,
 			write_or_die(fd, tag_template, strlen(tag_template));
 		close(fd);
 
-		launch_editor(path, buf);
+		launch_editor(path, buf, NULL);
 
 		unlink(path);
 		free(path);

strbuf.h

@@ -117,6 +117,6 @@ extern int strbuf_read_file(struct strbuf *sb, const char *path, size_t hint);
 extern int strbuf_getline(struct strbuf *, FILE *, int);
 
 extern void stripspace(struct strbuf *buf, int skip_comments);
-extern void launch_editor(const char *path, struct strbuf *buffer);
+extern void launch_editor(const char *path, struct strbuf *buffer, const char *const *env);
 
 #endif /* STRBUF_H */