fsmonitor: store fsmonitor bitmap before splitting index

ba1b9cac ("fsmonitor: delay updating state until after split index
is merged", 2017-10-27) resolved the problem of the fsmonitor data
being applied to the non-base index when reading; however, a similar
problem exists when writing the index.  Specifically, writing of the
fsmonitor extension happens only after the work to split the index
has been applied -- as such, the information in the index is only
for the non-"base" index, and thus the extension information
contains only partial data.

When saving, compute the ewah bitmap before the index is split, and
store it in the fsmonitor_dirty field, mirroring the behavior that
occurred during reading.  fsmonitor_dirty is kept from being leaked by
being freed when the extension data is written -- which always happens
precisely once, no matter the split index configuration.

Signed-off-by: Alex Vandiver <alexmv@dropbox.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 13 insertions, 0 deletions

diff --git a/t/t7519-status-fsmonitor.sh b/t/t7519-status-fsmonitor.sh
index c6df85af5e..eb2d13bbcf 100755
--- a/t/t7519-status-fsmonitor.sh
+++ b/t/t7519-status-fsmonitor.sh
@@ -301,4 +301,17 @@ do
 	done
 done
 
+# test that splitting the index dosn't interfere
+test_expect_success 'splitting the index results in the same state' '
+	write_integration_script &&
+	dirty_repo &&
+	git update-index --fsmonitor  &&
+	git ls-files -f >expect &&
+	test-dump-fsmonitor >&2 && echo &&
+	git update-index --fsmonitor --split-index &&
+	test-dump-fsmonitor >&2 && echo &&
+	git ls-files -f >actual &&
+	test_cmp expect actual
+'
+
 test_done