Fix fsmonitor after discard_index()

It was reported by Ævar Arnfjörð Bjarmason
[https://public-inbox.org/git/[email protected]/T/#mb8718fe52e4721dacd3b143a09187ff9090ef4e3]
that there were problems with the fsmonitor feature in conjunction with the newly built-in git stash/git rebase.

The culprit really is that the fsmonitor flag that says whether it was queried already was not re-set after discard_index() was called by mistake.

This fixes that, and apparently also other long-standing fsmonitor issues.

(Note that there is still a flakiness around t7519
[https://github.com/git-for-windows/git/pull/2127#pullrequestreview-215010574]
where it tries to make sure that the fsmonitor hook can prevent unnecessary lstat() calls, but that seems to be unrelated to this here bug.)

Changes since v1:

* Removed unnecessary test_when_finished "test_config ..." line, pointed out by Hannes Sixt.

Johannes Schindelin (2):
fsmonitor: demonstrate that it is not refreshed after discard_index()
fsmonitor: force a refresh after the index was discarded

 cache.h                     |  3 ++-
 fsmonitor.c                 |  5 ++---
 read-cache.c                |  1 +
 t/helper/test-read-cache.c  | 24 +++++++++++++++++++++++-
 t/t7519-status-fsmonitor.sh |  8 ++++++++
 5 files changed, 36 insertions(+), 5 deletions(-)

base-commit: 041f5ea1cf987a4068ef5f39ba0a09be85952064
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-165%2Fdscho%2Ffix-fsmonitor-after-discard-index-v2
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-165/dscho/fix-fsmonitor-after-discard-index-v2
Pull-Request: https://github.com/gitgitgadget/git/pull/165

Range-diff vs v1:

1: f451752656 ! 1: 51a7edf22a fsmonitor: demonstrate that it is not refreshed after discard_index()

     @@ -79,8 +79,6 @@
       '
       
      +test_expect_failure 'discard_index() also discards fsmonitor info' '
     -+	test_when_finished \
     -+		"git config core.monitor .git/hooks/fsmonitor-test" &&
      +	test_config core.fsmonitor "$TEST_DIRECTORY/t7519/fsmonitor-all" &&
      +	test_might_fail git update-index --refresh &&
      +	test-tool read-cache --print-and-refresh=tracked 2 >actual &&

2: 1d62623776 ! 2: 79fdd0d586 fsmonitor: force a refresh after the index was discarded
@@ -70,6 +70,6 @@

-test_expect_failure 'discard_index() also discards fsmonitor info' ' +test_expect_success 'discard_index() also discards fsmonitor info' '
- test_when_finished \
- "git config core.monitor .git/hooks/fsmonitor-test" &&
test_config core.fsmonitor "$TEST_DIRECTORY/t7519/fsmonitor-all" &&
+ test_might_fail git update-index --refresh &&
+ test-tool read-cache --print-and-refresh=tracked 2 >actual &&

gitgitgadget