am: make direct call to mailinfo

And finally the endgame.  Instead of spawning "git mailinfo" via the
run_command() API the same number of times as there are incoming
patches, make direct internal call to the libified mailinfo() from
"git am" to reduce the spawning overhead, which would matter on some
platforms.

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

builtin/am.c

@@ -27,6 +27,7 @@
 #include "notes-utils.h"
 #include "rerere.h"
 #include "prompt.h"
+#include "mailinfo.h"
 
 /**
  * Returns 1 if the file is empty or does not exist, 0 otherwise.
@@ -1258,58 +1259,61 @@ static void am_append_signoff(struct am_state *state)
 static int parse_mail(struct am_state *state, const char *mail)
 {
 	FILE *fp;
-	struct child_process cp = CHILD_PROCESS_INIT;
 	struct strbuf sb = STRBUF_INIT;
 	struct strbuf msg = STRBUF_INIT;
 	struct strbuf author_name = STRBUF_INIT;
 	struct strbuf author_date = STRBUF_INIT;
 	struct strbuf author_email = STRBUF_INIT;
 	int ret = 0;
+	struct mailinfo mi;
 
-	cp.git_cmd = 1;
-	cp.in = xopen(mail, O_RDONLY, 0);
-	cp.out = xopen(am_path(state, "info"), O_WRONLY | O_CREAT, 0777);
+	setup_mailinfo(&mi);
 
-	argv_array_push(&cp.args, "mailinfo");
-	argv_array_push(&cp.args, state->utf8 ? "-u" : "-n");
+	if (state->utf8)
+		mi.metainfo_charset = get_commit_output_encoding();
+	else
+		mi.metainfo_charset = NULL;
 
 	switch (state->keep) {
 	case KEEP_FALSE:
 		break;
 	case KEEP_TRUE:
-		argv_array_push(&cp.args, "-k");
+		mi.keep_subject = 1;
 		break;
 	case KEEP_NON_PATCH:
-		argv_array_push(&cp.args, "-b");
+		mi.keep_non_patch_brackets_in_subject = 1;
 		break;
 	default:
 		die("BUG: invalid value for state->keep");
 	}
 
 	if (state->message_id)
-		argv_array_push(&cp.args, "-m");
+		mi.add_message_id = 1;
 
 	switch (state->scissors) {
 	case SCISSORS_UNSET:
 		break;
 	case SCISSORS_FALSE:
-		argv_array_push(&cp.args, "--no-scissors");
+		mi.use_scissors = 0;
 		break;
 	case SCISSORS_TRUE:
-		argv_array_push(&cp.args, "--scissors");
+		mi.use_scissors = 1;
 		break;
 	default:
 		die("BUG: invalid value for state->scissors");
 	}
 
-	argv_array_push(&cp.args, am_path(state, "msg"));
-	argv_array_push(&cp.args, am_path(state, "patch"));
-
-	if (run_command(&cp) < 0)
+	mi.input = fopen(mail, "r");
+	if (!mi.input)
+		die("could not open input");
+	mi.output = fopen(am_path(state, "info"), "w");
+	if (!mi.output)
+		die("could not open output 'info'");
+	if (mailinfo(&mi, am_path(state, "msg"), am_path(state, "patch")))
 		die("could not parse patch");
 
-	close(cp.in);
-	close(cp.out);
+	fclose(mi.input);
+	fclose(mi.output);
 
 	/* Extract message and author information */
 	fp = xfopen(am_path(state, "info"), "r");
@@ -1341,8 +1345,7 @@ static int parse_mail(struct am_state *state, const char *mail)
 	}
 
 	strbuf_addstr(&msg, "\n\n");
-	if (strbuf_read_file(&msg, am_path(state, "msg"), 0) < 0)
-		die_errno(_("could not read '%s'"), am_path(state, "msg"));
+	strbuf_addbuf(&msg, &mi.log_message);
 	stripspace(&msg, 0);
 
 	if (state->signoff)
@@ -1366,6 +1369,7 @@ static int parse_mail(struct am_state *state, const char *mail)
 	strbuf_release(&author_email);
 	strbuf_release(&author_name);
 	strbuf_release(&sb);
+	clear_mailinfo(&mi);
 	return ret;
 }