gvfs-helper: skip collision check for loose objects

When we are installing a loose object, finalize_object_file() first
checks to see if the contents match what already exists in a loose
object file of the target name. However, this doesn't check if the
target is valid, it assumes the target is valid.

However, in the case of a power outage or something like that, the file
may be corrupt (for example: all NUL bytes). That is a common occurrence
when we are needing to install a loose object _again_: we don't think we
have it already so any copy that exists is probably bogus.

Use the flagged version with FOF_SKIP_COLLISION_CHECK to avoid these
types of errors, as seen in GitHub issue
microsoft#837.

Signed-off-by: Derrick Stolee <stolee@gmail.com>

Author: derrickstolee

gvfs-helper.c

@@ -2459,7 +2459,16 @@ static void install_loose(struct gh__request_params *params,
 		goto cleanup;
 	}
 
-	if (finalize_object_file(the_repository, tmp_path.buf, loose_path.buf)) {
+	/*
+	 * We skip collision check because the loose object in the target
+	 * may be corrupt and we should override it with a better value
+	 * instead of failing at this point.
+	 *
+	 * See https://github.com/microsoft/git/issues/837
+	 */
+	if (finalize_object_file_flags(the_repository,
+				       tmp_path.buf, loose_path.buf,
+				       FOF_SKIP_COLLISION_CHECK)) {
 		unlink(tmp_path.buf);
 		strbuf_addf(&status->error_message,
 			    "could not install loose object '%s'",