rev-list: teach --no-object-names to enable piping

Allow easier parsing by cat-file by giving rev-list an option to print
only the OID of a non-commit object without any additional information.
This is a short-term shim; later on, rev-list should be taught how to
print the types of objects it finds in a format similar to cat-file's.

Before this commit, the output from rev-list needed to be massaged
before being piped to cat-file, like so:

  git rev-list --objects HEAD | cut -f 1 -d ' ' |
    git cat-file --batch-check

This was especially unexpected when dealing with root trees, as an
invisible whitespace exists at the end of the OID:

  git rev-list --objects --filter=tree:1 --max-count=1 HEAD |
    xargs -I% echo "AA%AA"

Now, it can be piped directly, as in the added test case:

  git rev-list --objects --no-object-names HEAD | git cat-file --batch-check

Signed-off-by: Emily Shaffer <emilyshaffer@google.com>
Change-Id: I489bdf0a8215532e540175188883ff7541d70e1b
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 18 insertions, 1 deletions

diff --git a/builtin/rev-list.c b/builtin/rev-list.c
index 660172b014..301ccb970b 100644
--- a/builtin/rev-list.c
+++ b/builtin/rev-list.c
@@ -49,6 +49,7 @@ static const char rev_list_usage[] =
 "    --objects | --objects-edge\n"
 "    --unpacked\n"
 "    --header | --pretty\n"
+"    --[no-]object-names\n"
 "    --abbrev=<n> | --no-abbrev\n"
 "    --abbrev-commit\n"
 "    --left-right\n"
@@ -75,6 +76,9 @@ enum missing_action {
 };
 static enum missing_action arg_missing_action;
 
+/* display only the oid of each object encountered */
+static int arg_show_object_names = 1;
+
 #define DEFAULT_OIDSET_SIZE     (16*1024)
 
 static void finish_commit(struct commit *commit);
@@ -255,7 +259,10 @@ static void show_object(struct object *obj, const char *name, void *cb_data)
 	display_progress(progress, ++progress_counter);
 	if (info->flags & REV_LIST_QUIET)
 		return;
-	show_object_with_name(stdout, obj, name);
+	if (arg_show_object_names)
+		show_object_with_name(stdout, obj, name);
+	else
+		printf("%s\n", oid_to_hex(&obj->oid));
 }
 
 static void show_edge(struct commit *commit)
@@ -484,6 +491,16 @@ int cmd_rev_list(int argc, const char **argv, const char *prefix)
 		if (skip_prefix(arg, "--missing=", &arg))
 			continue; /* already handled above */
 
+		if (!strcmp(arg, ("--no-object-names"))) {
+			arg_show_object_names = 0;
+			continue;
+		}
+
+		if (!strcmp(arg, ("--object-names"))) {
+			arg_show_object_names = 1;
+			continue;
+		}
+
 		usage(rev_list_usage);
 
 	}