fsmonitor: force index write after full scan

fsmonitor currently only flags the index as dirty if the extension is being added or removed. This is a performance optimization that recognizes you can stat() a lot of files in less time than it takes to write out an updated index.

This patch makes a small enhancement and flags the index dirty if we end up having to stat() all files and scan the entire working directory. The assumption being that must be expensive or you would not have turned on the feature.

---

Notes:

    Base Ref:
    Web-Diff: https://github.com/benpeart/git/commit/4d39ddc2f9
    Checkout: git fetch https://github.com/benpeart/git fsmonitor-perf-v1 && git checkout 4d39ddc2f9

 fsmonitor.c | 3 +++
 1 file changed, 3 insertions(+)

index eb4e642256..ed3d1a074d 100644
@@ -185,6 +185,9 @@ void refresh_fsmonitor(struct index_state *istate)
 		for (i = 0; i < istate->cache_nr; i++)
 			istate->cache[i]->ce_flags &= ~CE_FSMONITOR_VALID;
 
+		/* If we're going to check every file, ensure we save the results */
+		istate->cache_changed |= FSMONITOR_CHANGED;
+
 		if (istate->untracked)
 			istate->untracked->use_fsmonitor = 0;
 	}

base-commit: 0ac4dfac5000ef8de7966a3b7229275567d2d707

2.17.0.windows.1