commit-graph: drop COMMIT_GRAPH_WRITE_CHECK_OIDS flag

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 "not-a-commit:"$1 }
        /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.

Helped-by: Jeff King <peff@peff.net>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 1 insertions, 3 deletions

diff --git a/commit-graph.h b/commit-graph.h
index 4212766..3ba0da1 100644
--- a/commit-graph.h
+++ b/commit-graph.h
@@ -91,9 +91,7 @@ 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_BLOOM_FILTERS = (1 << 3),
 };
 
 enum commit_graph_split_flags {