[PATCH 21/26] mailinfo: keep the parsed log message in a strbuf

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

When mailinfo() is eventually libified, the calling "git am" still
will have to write out the log message in the "msg" file for hooks
and other users of the information, but at least it does not have to
reopen and reread what was written back if the function kept it in a
strbuf so that the caller can read it from there.

This also removes the need for seeking and truncating the output
file when we see a scissors mark in the input, which in turn reduces
two callsites of die_errno().

Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 builtin/mailinfo.c | 41 ++++++++++++++++++++++++++++-------------
 1 file changed, 28 insertions(+), 13 deletions(-)

diff --git a/builtin/mailinfo.c b/builtin/mailinfo.c
index c9629c8..d38d716 100644
--- a/builtin/mailinfo.c
+++ b/builtin/mailinfo.c
@@ -10,7 +10,6 @@
 struct mailinfo {
 	FILE *input;
 	FILE *output;
-	FILE *cmitmsg;
 	FILE *patchfile;
 
 	struct strbuf name;
@@ -32,6 +31,8 @@ struct mailinfo {
 	int header_stage; /* still checking in-body headers? */
 	struct strbuf **p_hdr_data;
 	struct strbuf **s_hdr_data;
+
+	struct strbuf log_message;
 };
 
 #define MAX_HDR_PARSED 10
@@ -775,10 +776,8 @@ static int handle_commit_msg(struct mailinfo *mi, struct strbuf *line)
 
 	if (mi->use_scissors && is_scissors_line(line)) {
 		int i;
-		if (fseek(mi->cmitmsg, 0L, SEEK_SET))
-			die_errno("Could not rewind output message file");
-		if (ftruncate(fileno(mi->cmitmsg), 0))
-			die_errno("Could not truncate output message file at scissors");
+
+		strbuf_setlen(&mi->log_message, 0);
 		mi->header_stage = 1;
 
 		/*
@@ -795,13 +794,12 @@ static int handle_commit_msg(struct mailinfo *mi, struct strbuf *line)
 
 	if (patchbreak(line)) {
 		if (mi->message_id)
-			fprintf(mi->cmitmsg, "Message-Id: %s\n", mi->message_id);
-		fclose(mi->cmitmsg);
-		mi->cmitmsg = NULL;
+			strbuf_addf(&mi->log_message,
+				    "Message-Id: %s\n", mi->message_id);
 		return 1;
 	}
 
-	fputs(line->buf, mi->cmitmsg);
+	strbuf_addbuf(&mi->log_message, line);
 	return 0;
 }
 
@@ -999,18 +997,19 @@ static void handle_info(struct mailinfo *mi)
 
 static int mailinfo(struct mailinfo *mi, const char *msg, const char *patch)
 {
+	FILE *cmitmsg;
 	int peek;
 	struct strbuf line = STRBUF_INIT;
 
-	mi->cmitmsg = fopen(msg, "w");
-	if (!mi->cmitmsg) {
+	cmitmsg = fopen(msg, "w");
+	if (!cmitmsg) {
 		perror(msg);
 		return -1;
 	}
 	mi->patchfile = fopen(patch, "w");
 	if (!mi->patchfile) {
 		perror(patch);
-		fclose(mi->cmitmsg);
+		fclose(cmitmsg);
 		return -1;
 	}
 
@@ -1029,6 +1028,9 @@ static int mailinfo(struct mailinfo *mi, const char *msg, const char *patch)
 	handle_body(mi, &line);
 	handle_info(mi);
 
+	fwrite(mi->log_message.buf, 1, mi->log_message.len, cmitmsg);
+	fclose(cmitmsg);
+
 	return 0;
 }
 
@@ -1052,11 +1054,20 @@ static void setup_mailinfo(struct mailinfo *mi)
 	strbuf_init(&mi->name, 0);
 	strbuf_init(&mi->email, 0);
 	strbuf_init(&mi->charset, 0);
+	strbuf_init(&mi->log_message, 0);
 	mi->header_stage = 1;
 	mi->use_inbody_headers = 1;
 	git_config(git_mailinfo_config, &mi);
 }
 
+static void clear_mailinfo(struct mailinfo *mi)
+{
+	strbuf_release(&mi->name);
+	strbuf_release(&mi->email);
+	strbuf_release(&mi->charset);
+	strbuf_release(&mi->log_message);
+}
+
 static const char mailinfo_usage[] =
 	"git mailinfo [-k | -b] [-m | --message-id] [-u | --encoding=<encoding> | -n] [--scissors | --no-scissors] <msg> <patch> < mail >info";
 
@@ -1064,6 +1075,7 @@ int cmd_mailinfo(int argc, const char **argv, const char *prefix)
 {
 	const char *def_charset;
 	struct mailinfo mi;
+	int status;
 
 	/* NEEDSWORK: might want to do the optional .git/ directory
 	 * discovery
@@ -1102,5 +1114,8 @@ int cmd_mailinfo(int argc, const char **argv, const char *prefix)
 
 	mi.input = stdin;
 	mi.output = stdout;
-	return !!mailinfo(&mi, argv[1], argv[2]);
+	status = !!mailinfo(&mi, argv[1], argv[2]);
+	clear_mailinfo(&mi);
+
+	return status;
 }
-- 
2.6.1-320-g86a1181