Re: [PATCH v2 2/5] p0008-abbrev.sh: Test find_unique_abbrev() perf

On Thu, Oct 05, 2017 at 04:55:53AM -0400, Jeff King wrote:

On Mon, Sep 25, 2017 at 05:54:49AM -0400, Derrick Stolee wrote:

quoted

Create helper program test-abbrev to compute the minimum length of a
disambiguating short-sha for an input list of object ids.

This seems like something that Git ought to be able to do via real
commands.

Using "log --stdin --no-walk --format=%h" doesn't quite work, since it
only handles commits. We ought to be able to ask "cat-file" for this,
though. E.g., with the patch below you can do:

  git cat-file --batch-check='%(objectsize:short)' <input

Or even just dispense with your earlier randomization helper and do:

  git cat-file --batch-all-objects --batch-check='%(objectsize:short)'

to compute the abbreviation for every object.

Of course it would help if I bothered to include the patch. Here it is.

diff --git a/builtin/cat-file.c b/builtin/cat-file.c
index f5fa4fd75a..a5f911a632 100644
--- a/builtin/cat-file.c
+++ b/builtin/cat-file.c

@@ -225,6 +225,9 @@ static void expand_atom(struct strbuf *sb, const char *atom, int len,
 	if (is_atom("objectname", atom, len)) {
 		if (!data->mark_query)
 			strbuf_addstr(sb, oid_to_hex(&data->oid));
+	} else if (is_atom("objectname:short", atom, len)) {
+		if (!data->mark_query)
+			strbuf_add_unique_abbrev(sb, data->oid.hash, MINIMUM_ABBREV);
 	} else if (is_atom("objecttype", atom, len)) {
 		if (data->mark_query)
 			data->info.typep = &data->type;

-Peff