logmsg_reencode: never return NULL

The logmsg_reencode function will return the reencoded
commit buffer, or NULL if reencoding failed or no reencoding
was necessary. Since every caller then ends up checking for NULL
and just using the commit's original buffer, anyway, we can
be a bit more helpful and just return that buffer when we
would have returned NULL.

Since the resulting string may or may not need to be freed,
we introduce a logmsg_free, which checks whether the buffer
came from the commit object or not (callers either
implemented the same check already, or kept two separate
pointers, one to mark the buffer to be used, and one for the
to-be-freed string).

Pushing this logic into logmsg_* simplifies the callers, and
will let future patches lazily load the commit buffer in a
single place.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 22 insertions, 16 deletions

diff --git a/pretty.c b/pretty.c
index 07fc06286..c67534943 100644
--- a/pretty.c
+++ b/pretty.c
@@ -524,10 +524,11 @@ static void add_merge_info(const struct pretty_print_context *pp,
 	strbuf_addch(sb, '\n');
 }
 
-static char *get_header(const struct commit *commit, const char *key)
+static char *get_header(const struct commit *commit, const char *msg,
+			const char *key)
 {
 	int key_len = strlen(key);
-	const char *line = commit->buffer;
+	const char *line = msg;
 
 	while (line) {
 		const char *eol = strchr(line, '\n'), *next;
@@ -588,17 +589,18 @@ char *logmsg_reencode(const struct commit *commit,
 	static const char *utf8 = "UTF-8";
 	const char *use_encoding;
 	char *encoding;
+	char *msg = commit->buffer;
 	char *out;
 
 	if (!output_encoding || !*output_encoding)
-		return NULL;
-	encoding = get_header(commit, "encoding");
+		return msg;
+	encoding = get_header(commit, msg, "encoding");
 	use_encoding = encoding ? encoding : utf8;
 	if (same_encoding(use_encoding, output_encoding))
 		if (encoding) /* we'll strip encoding header later */
 			out = xstrdup(commit->buffer);
 		else
-			return NULL; /* nothing to do */
+			return msg; /* nothing to do */
 	else
 		out = reencode_string(commit->buffer,
 				      output_encoding, use_encoding);
@@ -606,7 +608,17 @@ char *logmsg_reencode(const struct commit *commit,
 		out = replace_encoding_header(out, output_encoding);
 
 	free(encoding);
-	return out;
+	/*
+	 * If the re-encoding failed, out might be NULL here; in that
+	 * case we just return the commit message verbatim.
+	 */
+	return out ? out : msg;
+}
+
+void logmsg_free(char *msg, const struct commit *commit)
+{
+	if (msg != commit->buffer)
+		free(msg);
 }
 
 static int mailmap_name(const char **email, size_t *email_len,
@@ -1278,14 +1290,11 @@ void format_commit_message(const struct commit *commit,
 	context.pretty_ctx = pretty_ctx;
 	context.wrap_start = sb->len;
 	context.message = logmsg_reencode(commit, output_enc);
-	if (!context.message)
-		context.message = commit->buffer;
 
 	strbuf_expand(sb, format, format_commit_item, &context);
 	rewrap_message_tail(sb, &context, 0, 0, 0);
 
-	if (context.message != commit->buffer)
-		free(context.message);
+	logmsg_free(context.message, commit);
 	free(context.signature.gpg_output);
 	free(context.signature.signer);
 }
@@ -1432,7 +1441,7 @@ void pretty_print_commit(const struct pretty_print_context *pp,
 {
 	unsigned long beginning_of_body;
 	int indent = 4;
-	const char *msg = commit->buffer;
+	const char *msg;
 	char *reencoded;
 	const char *encoding;
 	int need_8bit_cte = pp->need_8bit_cte;
@@ -1443,10 +1452,7 @@ void pretty_print_commit(const struct pretty_print_context *pp,
 	}
 
 	encoding = get_log_output_encoding();
-	reencoded = logmsg_reencode(commit, encoding);
-	if (reencoded) {
-		msg = reencoded;
-	}
+	msg = reencoded = logmsg_reencode(commit, encoding);
 
 	if (pp->fmt == CMIT_FMT_ONELINE || pp->fmt == CMIT_FMT_EMAIL)
 		indent = 0;
@@ -1503,7 +1509,7 @@ void pretty_print_commit(const struct pretty_print_context *pp,
 	if (pp->fmt == CMIT_FMT_EMAIL && sb->len <= beginning_of_body)
 		strbuf_addch(sb, '\n');
 
-	free(reencoded);
+	logmsg_free(reencoded, commit);
 }
 
 void pp_commit_easy(enum cmit_fmt fmt, const struct commit *commit,