format-patch: construct patch filename in one function

reopen_stdout() usually takes the oneline subject of a commit,
appends the patch suffix, prepends the output directory (if any) and
then reopens stdout as the resulting file. Now the patch filename (the
oneline subject and the patch suffix) is created in
get_patch_filename() and passed to reopen_stdout() which prepends the
output directory and reopens stdout as that file.

The original function to get the oneline description,
get_oneline_for_filename(), has been renamed to get_patch_filename() to
reflect its new functionality.

Signed-off-by: Stephen Boyd <bebarino@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin-log.c

@@ -419,12 +419,6 @@ int cmd_log(int argc, const char **argv, const char *prefix)
 /* format-patch */
 #define FORMAT_PATCH_NAME_MAX 64
 
-static int istitlechar(char c)
-{
-	return (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') ||
-		(c >= '0' && c <= '9') || c == '.' || c == '_';
-}
-
 static const char *fmt_patch_suffix = ".patch";
 static int numbered = 0;
 static int auto_number = 1;
@@ -519,61 +513,33 @@ static int git_format_config(const char *var, const char *value, void *cb)
 }
 
 
-static const char *get_oneline_for_filename(struct commit *commit,
-					    int keep_subject)
+static void get_patch_filename(struct commit *commit, int nr,
+			       const char *suffix, struct strbuf *buf)
 {
-	static char filename[PATH_MAX];
-	char *sol;
-	int len = 0;
-	int suffix_len = strlen(fmt_patch_suffix) + 1;
-
-	sol = strstr(commit->buffer, "\n\n");
-	if (!sol)
-		filename[0] = '\0';
-	else {
-		int j, space = 0;
-
-		sol += 2;
-		/* strip [PATCH] or [PATCH blabla] */
-		if (!keep_subject && !prefixcmp(sol, "[PATCH")) {
-			char *eos = strchr(sol + 6, ']');
-			if (eos) {
-				while (isspace(*eos))
-					eos++;
-				sol = eos;
-			}
-		}
+	int suffix_len = strlen(suffix) + 1;
+	int start_len = buf->len;
 
-		for (j = 0;
-		     j < FORMAT_PATCH_NAME_MAX - suffix_len - 5 &&
-			     len < sizeof(filename) - suffix_len &&
-			     sol[j] && sol[j] != '\n';
-		     j++) {
-			if (istitlechar(sol[j])) {
-				if (space) {
-					filename[len++] = '-';
-					space = 0;
-				}
-				filename[len++] = sol[j];
-				if (sol[j] == '.')
-					while (sol[j + 1] == '.')
-						j++;
-			} else
-				space = 1;
-		}
-		while (filename[len - 1] == '.'
-		       || filename[len - 1] == '-')
-			len--;
-		filename[len] = '\0';
+	strbuf_addf(buf, commit ? "%04d-" : "%d", nr);
+	if (commit) {
+		format_commit_message(commit, "%f", buf, DATE_NORMAL);
+		/*
+		 * Replace characters at the end with the suffix if the
+		 * filename is too long
+		 */
+		if (buf->len + suffix_len > FORMAT_PATCH_NAME_MAX + start_len)
+			strbuf_splice(buf,
+				start_len + FORMAT_PATCH_NAME_MAX - suffix_len,
+				suffix_len, suffix, suffix_len);
+		else
+			strbuf_addstr(buf, suffix);
 	}
-	return filename;
 }
 
 static FILE *realstdout = NULL;
 static const char *output_directory = NULL;
 static int outdir_offset;
 
-static int reopen_stdout(const char *oneline, int nr, struct rev_info *rev)
+static int reopen_stdout(const char *oneline, struct rev_info *rev)
 {
 	char filename[PATH_MAX];
 	int len = 0;
@@ -589,14 +555,7 @@ static int reopen_stdout(const char *oneline, int nr, struct rev_info *rev)
 			filename[len++] = '/';
 	}
 
-	if (!oneline)
-		len += sprintf(filename + len, "%d", nr);
-	else {
-		len += sprintf(filename + len, "%04d-", nr);
-		len += snprintf(filename + len, sizeof(filename) - len - 1
-				- suffix_len, "%s", oneline);
-		strcpy(filename + len, fmt_patch_suffix);
-	}
+	strncpy(filename + len, oneline, PATH_MAX - len);
 
 	if (!DIFF_OPT_TST(&rev->diffopt, QUIET))
 		fprintf(realstdout, "%s\n", filename + outdir_offset);
@@ -684,12 +643,17 @@ static void make_cover_letter(struct rev_info *rev, int use_stdout,
 	const char *encoding = "utf-8";
 	struct diff_options opts;
 	int need_8bit_cte = 0;
+	char filename[PATH_MAX];
 
 	if (rev->commit_format != CMIT_FMT_EMAIL)
 		die("Cover letter needs email format");
 
-	if (!use_stdout && reopen_stdout(numbered_files ?
-				NULL : "cover-letter", 0, rev))
+	if (numbered_files)
+		sprintf(filename, "0");
+	else
+		sprintf(filename, "%04d-cover-letter%s", 0, fmt_patch_suffix);
+
+	if (!use_stdout && reopen_stdout(filename, rev))
 		return;
 
 	head_sha1 = sha1_to_hex(head->object.sha1);
@@ -802,6 +766,7 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
 	struct patch_ids ids;
 	char *add_signoff = NULL;
 	struct strbuf buf = STRBUF_INIT;
+	struct strbuf patch_filename = STRBUF_INIT;
 
 	git_config(git_format_config, NULL);
 	init_revisions(&rev, prefix);
@@ -1104,10 +1069,12 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
 			}
 			gen_message_id(&rev, sha1_to_hex(commit->object.sha1));
 		}
-		if (!use_stdout && reopen_stdout(numbered_files ? NULL :
-				get_oneline_for_filename(commit, keep_subject),
-				rev.nr, &rev))
+
+		get_patch_filename(numbered_files ? NULL : commit, rev.nr,
+				    fmt_patch_suffix, &patch_filename);
+		if (!use_stdout && reopen_stdout(patch_filename.buf, &rev))
 			die("Failed to create output files");
+		strbuf_setlen(&patch_filename, 0);
 		shown = log_tree_commit(&rev, commit);
 		free(commit->buffer);
 		commit->buffer = NULL;
@@ -1131,6 +1098,7 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
 		if (!use_stdout)
 			fclose(stdout);
 	}
+	strbuf_release(&patch_filename);
 	free(list);
 	if (ignore_if_in_upstream)
 		free_patch_ids(&ids);