commit: support alternate status formats

The status command recently grew "short" and "porcelain"
options for alternate output formats. Since status is no
longer "commit --dry-run", these formats are inaccessible to
people who do want to see a dry-run in a parseable form.

This patch makes those formats available to "git commit",
implying the "dry-run" option when they are used.

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

Documentation/git-commit.txt

@@ -75,6 +75,20 @@ OPTIONS
 	and paths that are untracked, similar to the one that is given
 	in the commit log editor.
 
+--short::
+	When doing a dry-run, give the output in the short-format. See
+	linkgit:git-status[1] for details. Implies `--dry-run`.
+
+--porcelain::
+	When doing a dry-run, give the output in a porcelain-ready
+	format. See linkgit:git-status[1] for details. Implies
+	`--dry-run`.
+
+-z::
+	When showing `short` or `porcelain` status output, terminate
+	entries in the status output with NUL, instead of LF. If no
+	format is given, implies the `--porcelain` output format.
+
 -F <file>::
 --file=<file>::
 	Take the commit message from the given file.  Use '-' to

builtin-commit.c

@@ -72,6 +72,15 @@ static int use_editor = 1, initial_commit, in_merge;
 static const char *only_include_assumed;
 static struct strbuf message;
 
+static int null_termination;
+static enum {
+	STATUS_FORMAT_LONG,
+	STATUS_FORMAT_SHORT,
+	STATUS_FORMAT_PORCELAIN,
+} status_format = STATUS_FORMAT_LONG;
+
+static void short_print(struct wt_status *s, int null_termination);
+
 static int opt_parse_m(const struct option *opt, const char *arg, int unset)
 {
 	struct strbuf *buf = opt->value;
@@ -105,6 +114,12 @@ static struct option builtin_commit_options[] = {
 	OPT_BOOLEAN('o', "only", &only, "commit only specified files"),
 	OPT_BOOLEAN('n', "no-verify", &no_verify, "bypass pre-commit hook"),
 	OPT_BOOLEAN(0, "dry-run", &dry_run, "show what would be committed"),
+	OPT_SET_INT(0, "short", &status_format, "show status concisely",
+		    STATUS_FORMAT_SHORT),
+	OPT_SET_INT(0, "porcelain", &status_format,
+		    "show porcelain output format", STATUS_FORMAT_PORCELAIN),
+	OPT_BOOLEAN('z', "null", &null_termination,
+		    "terminate entries with NUL"),
 	OPT_BOOLEAN(0, "amend", &amend, "amend previous commit"),
 	{ OPTION_STRING, 'u', "untracked-files", &untracked_files_arg, "mode", "show untracked files, optional modes: all, normal, no. (Default: all)", PARSE_OPT_OPTARG, NULL, (intptr_t)"all" },
 	OPT_BOOLEAN(0, "allow-empty", &allow_empty, "ok to record an empty change"),
@@ -363,7 +378,18 @@ static int run_status(FILE *fp, const char *index_file, const char *prefix, int
 	s->is_initial = get_sha1(s->reference, sha1) ? 1 : 0;
 
 	wt_status_collect(s);
-	wt_status_print(s);
+
+	switch (status_format) {
+	case STATUS_FORMAT_SHORT:
+		short_print(s, null_termination);
+		break;
+	case STATUS_FORMAT_PORCELAIN:
+		short_print(s, null_termination);
+		break;
+	case STATUS_FORMAT_LONG:
+		wt_status_print(s);
+		break;
+	}
 
 	return s->commitable;
 }
@@ -821,6 +847,11 @@ static int parse_and_validate_options(int argc, const char *argv[],
 	else if (interactive && argc > 0)
 		die("Paths with --interactive does not make sense.");
 
+	if (null_termination && status_format == STATUS_FORMAT_LONG)
+		status_format = STATUS_FORMAT_PORCELAIN;
+	if (status_format != STATUS_FORMAT_LONG)
+		dry_run = 1;
+
 	return argc;
 }
 
@@ -991,12 +1022,6 @@ static void short_print(struct wt_status *s, int null_termination)
 int cmd_status(int argc, const char **argv, const char *prefix)
 {
 	struct wt_status s;
-	static int null_termination;
-	static enum {
-		STATUS_FORMAT_LONG,
-		STATUS_FORMAT_SHORT,
-		STATUS_FORMAT_PORCELAIN,
-	} status_format = STATUS_FORMAT_LONG;
 	unsigned char sha1[20];
 	static struct option builtin_status_options[] = {
 		OPT__VERBOSE(&verbose),