Add custom subject prefix support to format-patch (take 3)

Add a new option to git-format-patch, entitled --subject-prefix that allows
control of the subject prefix '[PATCH]'. Using this option, the text 'PATCH' is
replaced with whatever input is provided to the option. This allows easily
generating patches like '[PATCH 2.6.21-rc3]' or properly numbered series like
'[-mm3 PATCH N/M]'. This patch provides the implementation and documentation.

Signed-off-by: Robin H. Johnson <robbat2@gentoo.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>

4 files changed, 31 insertions, 11 deletions

diff --git a/Documentation/git-format-patch.txt b/Documentation/git-format-patch.txt
index 111d7c60bf..a33d157b97 100644
--- a/Documentation/git-format-patch.txt
+++ b/Documentation/git-format-patch.txt
@@ -10,11 +10,12 @@ SYNOPSIS
 --------
 [verse]
 'git-format-patch' [-n | -k] [-o <dir> | --stdout] [--thread]
-	           [--attach[=<boundary>] | --inline[=<boundary>]]
-	           [-s | --signoff] [<common diff options>] [--start-number <n>]
-		   [--in-reply-to=Message-Id] [--suffix=.<sfx>]
-		   [--ignore-if-in-upstream]
-		   <since>[..<until>]
+                   [--attach[=<boundary>] | --inline[=<boundary>]]
+                   [-s | --signoff] [<common diff options>] [--start-number <n>]
+                   [--in-reply-to=Message-Id] [--suffix=.<sfx>]
+                   [--ignore-if-in-upstream]
+                   [--subject-prefix=Subject-Prefix]
+                   <since>[..<until>]
 
 DESCRIPTION
 -----------
@@ -98,6 +99,12 @@ include::diff-options.txt[]
 	patches being generated, and any patch that matches is
 	ignored.
 
+--subject-prefix=<Subject-Prefix>::
+	Instead of the standard '[PATCH]' prefix in the subject
+	line, instead use '[<Subject-Prefix>]'. This
+	allows for useful naming of a patch series, and can be
+	combined with the --numbered option.
+
 --suffix=.<sfx>::
 	Instead of using `.patch` as the suffix for generated
 	filenames, use specifed suffix.  A common alternative is
diff --git a/builtin-log.c b/builtin-log.c
index 71df957eaa..4a4890aca0 100644
--- a/builtin-log.c
+++ b/builtin-log.c
@@ -417,6 +417,7 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
 	int numbered = 0;
 	int start_number = -1;
 	int keep_subject = 0;
+	int subject_prefix = 0;
 	int ignore_if_in_upstream = 0;
 	int thread = 0;
 	const char *in_reply_to = NULL;
@@ -434,6 +435,7 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
 	rev.ignore_merges = 1;
 	rev.diffopt.msg_sep = "";
 	rev.diffopt.recursive = 1;
+	rev.subject_prefix = "PATCH";
 
 	rev.extra_headers = extra_headers;
 
@@ -509,8 +511,10 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
 			if (i == argc)
 				die("Need a Message-Id for --in-reply-to");
 			in_reply_to = argv[i];
-		}
-		else if (!prefixcmp(argv[i], "--suffix="))
+		} else if (!prefixcmp(argv[i], "--subject-prefix=")) {
+			subject_prefix = 1;
+			rev.subject_prefix = argv[i] + 17;
+		} else if (!prefixcmp(argv[i], "--suffix="))
 			fmt_patch_suffix = argv[i] + 9;
 		else
 			argv[j++] = argv[i];
@@ -521,6 +525,8 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
 		start_number = 1;
 	if (numbered && keep_subject)
 		die ("-n and -k are mutually exclusive.");
+	if (keep_subject && subject_prefix)
+		die ("--subject-prefix and -k are mutually exclusive.");
 
 	argc = setup_revisions(argc, argv, &rev, "HEAD");
 	if (argc > 1)
diff --git a/log-tree.c b/log-tree.c
index 8797aa14c4..dad5513230 100644
--- a/log-tree.c
+++ b/log-tree.c
@@ -165,14 +165,20 @@ void show_log(struct rev_info *opt, const char *sep)
 		if (opt->total > 0) {
 			static char buffer[64];
 			snprintf(buffer, sizeof(buffer),
-					"Subject: [PATCH %0*d/%d] ",
+					"Subject: [%s %0*d/%d] ",
+					opt->subject_prefix,
 					digits_in_number(opt->total),
 					opt->nr, opt->total);
 			subject = buffer;
-		} else if (opt->total == 0)
-			subject = "Subject: [PATCH] ";
-		else
+		} else if (opt->total == 0) {
+			static char buffer[256];
+			snprintf(buffer, sizeof(buffer),
+					"Subject: [%s] ",
+					opt->subject_prefix);
+			subject = buffer;
+		} else {
 			subject = "Subject: ";
+		}
 
 		printf("From %s Mon Sep 17 00:00:00 2001\n", sha1);
 		if (opt->message_id)
diff --git a/revision.h b/revision.h
index 55e6b531ce..5f3f628a9b 100644
--- a/revision.h
+++ b/revision.h
@@ -78,6 +78,7 @@ struct rev_info {
 	const char	*add_signoff;
 	const char	*extra_headers;
 	const char	*log_reencode;
+	const char	*subject_prefix;
 	int		no_inline;
 
 	/* Filter by commit log message */