commit: Allow skipping automatic summary generation

If a commit is being made during summary generation, then it would
trigger the summary to be generated again. That's either unwanted busy
work or could result in an infinite loop. Add a boolean in
`OstreeRepoTxn` to disable automatic summary generation as seen fit.

src/libostree/ostree-repo-commit.c

@@ -2350,7 +2350,8 @@ ostree_repo_commit_transaction (OstreeRepo                  *self,
   /* Update the summary if auto-update-summary is set, because doing so was
    * delayed for each ref change during the transaction.
    */
-  if ((self->txn.refs || self->txn.collection_refs) &&
+  if (!self->txn.disable_auto_summary &&
+      (self->txn.refs || self->txn.collection_refs) &&
       !_ostree_repo_maybe_regenerate_summary (self, cancellable, error))
     return FALSE;
 

src/libostree/ostree-repo-private.h

@@ -101,6 +101,7 @@ typedef struct {
   /* Implementation of min-free-space-percent */
   gulong blocksize;
   fsblkcnt_t max_blocks;
+  gboolean disable_auto_summary;
 } OstreeRepoTxn;
 
 typedef struct {