[PATCH 8/8] commit-graph: drop COMMIT_GRAPH_WRITE_CHECK_OIDS flag

[Taylor Blau <me@ttaylorr.com>]

Since 7c5c9b9c57 (commit-graph: error out on invalid commit oids in
'write --stdin-commits', 2019-08-05), the commit-graph builtin dies on
receiving non-commit OIDs as input to '--stdin-commits'.

This behavior can be cumbersome to work around in, say, the case of
piping 'git for-each-ref' to 'git commit-graph write --stdin-commits' if
the caller does not want to cull out non-commits themselves. In this
situation, it would be ideal if 'git commit-graph write' wrote the graph
containing the inputs that did pertain to commits, and silently ignored
the remainder of the input.

Some options have been proposed to the effect of '--[no-]check-oids'
which would allow callers to have the commit-graph builtin do just that.
After some discussion, it is difficult to imagine a caller who wouldn't
want to pass '--no-check-oids', suggesting that we should get rid of the
behavior of complaining about non-commit inputs altogether.

If callers do wish to retain this behavior, they can easily work around
this change by doing the following:

    git for-each-ref --format='%(objectname) %(objecttype) %(*objecttype)' |
    awk '/commit/ { print $1 }' |
    git commit-graph write --stdin-commits

To make it so that valid OIDs that refer to non-existent objects are
indeed an error after loosening the error handling, perform an extra
lookup to make sure that object indeed exists before sending it to the
commit-graph internals.

Signed-off-by: Taylor Blau <me@ttaylorr.com>
---
 Documentation/git-commit-graph.txt |  6 ++++--
 builtin/commit-graph.c             | 10 +++++-----
 commit-graph.c                     |  2 --
 commit-graph.h                     | 10 ++++------
 t/t5318-commit-graph.sh            | 15 +++++++++++----
 5 files changed, 24 insertions(+), 19 deletions(-)

diff --git a/Documentation/git-commit-graph.txt b/Documentation/git-commit-graph.txt
index 53a650225a..fcac7d12e1 100644
--- a/Documentation/git-commit-graph.txt
+++ b/Documentation/git-commit-graph.txt
@@ -47,8 +47,10 @@ with `--stdin-commits` or `--reachable`.)
 +
 With the `--stdin-commits` option, generate the new commit graph by
 walking commits starting at the commits specified in stdin as a list
-of OIDs in hex, one OID per line. (Cannot be combined with
-`--stdin-packs` or `--reachable`.)
+of OIDs in hex, one OID per line. OIDs that resolve to non-commits
+(either directly, or by peeling tags) are silently ignored. OIDs that
+are malformed, or do not exist generate an error. (Cannot be combined
+with `--stdin-packs` or `--reachable`.)
 +
 With the `--reachable` option, generate the new commit graph by walking
 commits starting at all refs. (Cannot be combined with `--stdin-commits`
diff --git a/builtin/commit-graph.c b/builtin/commit-graph.c
index 9eec68572f..3637d079fb 100644
--- a/builtin/commit-graph.c
+++ b/builtin/commit-graph.c
@@ -153,13 +153,14 @@ static int read_one_commit(struct oidset *commits, struct progress *progress,
 
 	display_progress(progress, oidset_size(commits) + 1);
 
+	if (oid_object_info(the_repository, &oid, NULL) < 0) {
+		error(_("object %s does not exist"), hash);
+		return 1;
+	}
+
 	result = lookup_commit_reference_gently(the_repository, &oid, 1);
 	if (result)
 		oidset_insert(commits, &result->object.oid);
-	else {
-		error(_("invalid commit object id: %s"), hash);
-		return 1;
-	}
 	return 0;
 }
 
@@ -239,7 +240,6 @@ static int graph_write(int argc, const char **argv)
 		struct strbuf buf = STRBUF_INIT;
 		if (opts.stdin_commits) {
 			oidset_init(&commits, 0);
-			flags |= COMMIT_GRAPH_WRITE_CHECK_OIDS;
 			if (opts.progress)
 				progress = start_delayed_progress(
 					_("Analyzing commits from stdin"), 0);
diff --git a/commit-graph.c b/commit-graph.c
index 24c2d80935..4e5539bac5 100644
--- a/commit-graph.c
+++ b/commit-graph.c
@@ -880,7 +880,6 @@ struct write_commit_graph_context {
 	unsigned append:1,
 		 report_progress:1,
 		 split:1,
-		 check_oids:1,
 		 changed_paths:1,
 		 order_by_pack:1;
 
@@ -2001,7 +2000,6 @@ int write_commit_graph(struct object_directory *odb,
 	ctx->append = flags & COMMIT_GRAPH_WRITE_APPEND ? 1 : 0;
 	ctx->report_progress = flags & COMMIT_GRAPH_WRITE_PROGRESS ? 1 : 0;
 	ctx->split = flags & COMMIT_GRAPH_WRITE_SPLIT ? 1 : 0;
-	ctx->check_oids = flags & COMMIT_GRAPH_WRITE_CHECK_OIDS ? 1 : 0;
 	ctx->split_opts = split_opts;
 	ctx->changed_paths = flags & COMMIT_GRAPH_WRITE_BLOOM_FILTERS ? 1 : 0;
 	ctx->total_bloom_filter_data_size = 0;
diff --git a/commit-graph.h b/commit-graph.h
index 4212766a4f..659393e07f 100644
--- a/commit-graph.h
+++ b/commit-graph.h
@@ -88,12 +88,10 @@ struct commit_graph *parse_commit_graph(void *graph_map, size_t graph_size);
 int generation_numbers_enabled(struct repository *r);
 
 enum commit_graph_write_flags {
-	COMMIT_GRAPH_WRITE_APPEND     = (1 << 0),
-	COMMIT_GRAPH_WRITE_PROGRESS   = (1 << 1),
-	COMMIT_GRAPH_WRITE_SPLIT      = (1 << 2),
-	/* Make sure that each OID in the input is a valid commit OID. */
-	COMMIT_GRAPH_WRITE_CHECK_OIDS = (1 << 3),
-	COMMIT_GRAPH_WRITE_BLOOM_FILTERS = (1 << 4),
+	COMMIT_GRAPH_WRITE_APPEND        = (1 << 0),
+	COMMIT_GRAPH_WRITE_PROGRESS      = (1 << 1),
+	COMMIT_GRAPH_WRITE_SPLIT         = (1 << 2),
+	COMMIT_GRAPH_WRITE_BLOOM_FILTERS = (1 << 3)
 };
 
 enum commit_graph_split_flags {
diff --git a/t/t5318-commit-graph.sh b/t/t5318-commit-graph.sh
index 89020d3d44..74f93f0a17 100755
--- a/t/t5318-commit-graph.sh
+++ b/t/t5318-commit-graph.sh
@@ -84,11 +84,18 @@ graph_read_expect() {
 
 test_expect_success 'exit with correct error on bad input to --stdin-commits' '
 	cd "$TRASH_DIRECTORY/full" &&
-	echo HEAD | test_expect_code 1 git commit-graph write --stdin-commits 2>stderr &&
+	# invalid, non-hex OID
+	echo HEAD >in &&
+	test_expect_code 1 git commit-graph write --stdin-commits <in 2>stderr &&
 	test_i18ngrep "unexpected non-hex object ID: HEAD" stderr &&
-	# valid tree OID, but not a commit OID
-	git rev-parse HEAD^{tree} | test_expect_code 1 git commit-graph write --stdin-commits 2>stderr &&
-	test_i18ngrep "invalid commit object id" stderr
+	# non-existent OID
+	echo $ZERO_OID >in &&
+	test_expect_code 1 git commit-graph write --stdin-commits <in 2>stderr &&
+	test_i18ngrep "does not exist" stderr &&
+	# valid commit and tree OID
+	git rev-parse HEAD HEAD^{tree} >in &&
+	git commit-graph write --stdin-commits <in &&
+	graph_read_expect 3
 '
 
 test_expect_success 'write graph' '
-- 
2.26.0.113.ge9739cdccc