rev-list: add option for --pretty=format without header

In general, we encourage users to use plumbing commands, like git
rev-list, over porcelain commands, like git log, when scripting.
However, git rev-list has one glaring problem that prevents it from
being used in certain cases: when --pretty is used with a custom format,
it always prints out a line containing "commit" and the object ID.  This
makes it unsuitable for many scripting needs, and forces users to use
git log instead.

While we can't change this behavior for backwards compatibility, we can
add an option to suppress this behavior, so let's do so, and call it
"--no-commit-header".  Additionally, add the corresponding positive
option to switch it back on.

Note that this option doesn't affect the built-in formats, only custom
formats.  This is exactly the same behavior as users already have from
git log and is what most users will be used to.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/rev-list-options.txt

@@ -1064,6 +1064,14 @@ ifdef::git-rev-list[]
 --header::
 	Print the contents of the commit in raw-format; each record is
 	separated with a NUL character.
+
+--no-commit-header::
+	Suppress the header line containing "commit" and the object ID printed before
+	the specified format.  This has no effect on the built-in formats; only custom
+	formats are affected.
+
+--commit-header::
+	Overrides a previous `--no-commit-header`.
 endif::git-rev-list[]
 
 --parents::

builtin/rev-list.c

@@ -127,13 +127,15 @@ static void show_commit(struct commit *commit, void *data)
 	if (info->header_prefix)
 		fputs(info->header_prefix, stdout);
 
-	if (!revs->graph)
-		fputs(get_revision_mark(revs, commit), stdout);
-	if (revs->abbrev_commit && revs->abbrev)
-		fputs(find_unique_abbrev(&commit->object.oid, revs->abbrev),
-		      stdout);
-	else
-		fputs(oid_to_hex(&commit->object.oid), stdout);
+	if (revs->include_header) {
+		if (!revs->graph)
+			fputs(get_revision_mark(revs, commit), stdout);
+		if (revs->abbrev_commit && revs->abbrev)
+			fputs(find_unique_abbrev(&commit->object.oid, revs->abbrev),
+			      stdout);
+		else
+			fputs(oid_to_hex(&commit->object.oid), stdout);
+	}
 	if (revs->print_parents) {
 		struct commit_list *parents = commit->parents;
 		while (parents) {
@@ -153,7 +155,7 @@ static void show_commit(struct commit *commit, void *data)
 	show_decorations(revs, commit);
 	if (revs->commit_format == CMIT_FMT_ONELINE)
 		putchar(' ');
-	else
+	else if (revs->include_header)
 		putchar('\n');
 
 	if (revs->verbose_header) {
@@ -512,6 +514,7 @@ int cmd_rev_list(int argc, const char **argv, const char *prefix)
 	repo_init_revisions(the_repository, &revs, prefix);
 	revs.abbrev = DEFAULT_ABBREV;
 	revs.commit_format = CMIT_FMT_UNSPECIFIED;
+	revs.include_header = 1;
 
 	/*
 	 * Scan the argument list before invoking setup_revisions(), so that we
@@ -627,6 +630,16 @@ int cmd_rev_list(int argc, const char **argv, const char *prefix)
 			continue;
 		}
 
+		if (!strcmp(arg, ("--commit-header"))) {
+			revs.include_header = 1;
+			continue;
+		}
+
+		if (!strcmp(arg, ("--no-commit-header"))) {
+			revs.include_header = 0;
+			continue;
+		}
+
 		if (!strcmp(arg, "--disk-usage")) {
 			show_disk_usage = 1;
 			info.flags |= REV_LIST_QUIET;
@@ -636,10 +649,12 @@ int cmd_rev_list(int argc, const char **argv, const char *prefix)
 		usage(rev_list_usage);
 
 	}
+	if (revs.commit_format != CMIT_FMT_USERFORMAT)
+		revs.include_header = 1;
 	if (revs.commit_format != CMIT_FMT_UNSPECIFIED) {
 		/* The command line has a --pretty  */
 		info.hdr_termination = '\n';
-		if (revs.commit_format == CMIT_FMT_ONELINE)
+		if (revs.commit_format == CMIT_FMT_ONELINE || !revs.include_header)
 			info.header_prefix = "";
 		else
 			info.header_prefix = "commit ";

revision.h

@@ -215,7 +215,8 @@ struct rev_info {
 			missing_newline:1,
 			date_mode_explicit:1,
 			preserve_subject:1,
-			encode_email_headers:1;
+			encode_email_headers:1,
+			include_header:1;
 	unsigned int	disable_stdin:1;
 	/* --show-linear-break */
 	unsigned int	track_linear:1,

t/t6006-rev-list-format.sh

@@ -41,22 +41,59 @@ test_expect_success 'setup' '
 	echo "$added_iso88591" | git commit -F - &&
 	head1=$(git rev-parse --verify HEAD) &&
 	head1_short=$(git rev-parse --verify --short $head1) &&
+	head1_short4=$(git rev-parse --verify --short=4 $head1) &&
 	tree1=$(git rev-parse --verify HEAD:) &&
 	tree1_short=$(git rev-parse --verify --short $tree1) &&
 	echo "$changed" > foo &&
 	echo "$changed_iso88591" | git commit -a -F - &&
 	head2=$(git rev-parse --verify HEAD) &&
 	head2_short=$(git rev-parse --verify --short $head2) &&
+	head2_short4=$(git rev-parse --verify --short=4 $head2) &&
 	tree2=$(git rev-parse --verify HEAD:) &&
 	tree2_short=$(git rev-parse --verify --short $tree2) &&
 	git config --unset i18n.commitEncoding
 '
 
-# usage: test_format name format_string [failure] <expected_output
+# usage: test_format [argument...] name format_string [failure] <expected_output
 test_format () {
+	local args=
+	while true
+	do
+		case "$1" in
+		--*)
+			args="$args $1"
+			shift;;
+		*)
+			break;;
+		esac
+	done
 	cat >expect.$1
 	test_expect_${3:-success} "format $1" "
-		git rev-list --pretty=format:'$2' main >output.$1 &&
+		git rev-list $args --pretty=format:'$2' main >output.$1 &&
+		test_cmp expect.$1 output.$1
+	"
+}
+
+# usage: test_pretty [argument...] name format_name [failure] <expected_output
+test_pretty () {
+	local args=
+	while true
+	do
+		case "$1" in
+		--*)
+			args="$args $1"
+			shift;;
+		*)
+			break;;
+		esac
+	done
+	cat >expect.$1
+	test_expect_${3:-success} "pretty $1 (without --no-commit-header)" "
+		git rev-list $args --pretty='$2' main >output.$1 &&
+		test_cmp expect.$1 output.$1
+	"
+	test_expect_${3:-success} "pretty $1 (with --no-commit-header)" "
+		git rev-list $args --no-commit-header --pretty='$2' main >output.$1 &&
 		test_cmp expect.$1 output.$1
 	"
 }
@@ -93,6 +130,20 @@ $head1
 $head1_short
 EOF
 
+test_format --no-commit-header hash-no-header %H%n%h <<EOF
+$head2
+$head2_short
+$head1
+$head1_short
+EOF
+
+test_format --abbrev-commit --abbrev=0 --no-commit-header hash-no-header-abbrev %H%n%h <<EOF
+$head2
+$head2_short4
+$head1
+$head1_short4
+EOF
+
 test_format tree %T%n%t <<EOF
 commit $head2
 $tree2
@@ -181,6 +232,31 @@ $added
 
 EOF
 
+test_format --no-commit-header raw-body-no-header %B <<EOF
+$changed
+
+$added
+
+EOF
+
+test_pretty oneline oneline <<EOF
+$head2 $changed
+$head1 $added
+EOF
+
+test_pretty short short <<EOF
+commit $head2
+Author: $GIT_AUTHOR_NAME <$GIT_AUTHOR_EMAIL>
+
+    $changed
+
+commit $head1
+Author: $GIT_AUTHOR_NAME <$GIT_AUTHOR_EMAIL>
+
+    $added
+
+EOF
+
 test_expect_success 'basic colors' '
 	cat >expect <<-EOF &&
 	commit $head2