This patch makes update-index --refresh write the index if it contains racy
timestamps, as discussed at [1].

Changes since v3:

 * test-lib: improve API for verifying file mtime
   * fix quoting around "$1"
   * use "rm -f" for cleanup of auxiliary files
   * improve API description comments
 * Note that gitgitgadget's "freebsd_12" check is failing since a couple of
   days (unrelated to this pull request); hence, this check hasn't been
   applied to this patch series

Changes since v2:

 * new patch: test-lib: introduce API for verifying file mtime
 * new patch: t7508: fix bogus mtime verification for test
   "--no-optional-locks prevents index update"
 * change new tests in t2108 and t7508 to use new test-lib mtime API
 * fix "--refresh has no racy timestamps to fix" to use +60s mtime to be
   save on VFAT

Changes since v1:

 * main commit message now uses 'git update-index' and the paragraph was
   dropped
 * t/t7508-status.sh: two tests added which capture status racy handling
 * builtin/update-index.c: comment improved
 * t/t2108-update-index-refresh-racy.sh: major overhaul
   * one test case added
   * mtime-manipulations simplified and aligned to t7508
   * code style fixes, as discussed

[1]
https://lore.kernel.org/git/d3dd805c-7c1d-30a9-6574-a7bfcb7fc013@syntevo.com/

Marc Strapetz (4):
  test-lib: introduce API for verifying file mtime
  t7508: fix bogus mtime verification
  t7508: add tests capturing racy timestamp handling
  update-index: refresh should rewrite index in case of racy timestamps

 builtin/update-index.c               | 11 +++++
 cache.h                              |  1 +
 read-cache.c                         |  2 +-
 t/t2108-update-index-refresh-racy.sh | 64 ++++++++++++++++++++++++++++
 t/t7508-status.sh                    | 30 ++++++++++---
 t/test-lib-functions.sh              | 33 ++++++++++++++
 6 files changed, 135 insertions(+), 6 deletions(-)
 create mode 100755 t/t2108-update-index-refresh-racy.sh

base-commit: dcc0cd074f0c639a0df20461a301af6d45bd582e

Submitted-As: https://lore.kernel.org/git/pull.1105.v4.git.1641554252.gitgitgadget@gmail.com
In-Reply-To: https://lore.kernel.org/git/pull.1105.git.1640181390841.gitgitgadget@gmail.com
In-Reply-To: https://lore.kernel.org/git/pull.1105.v2.git.1641388523.gitgitgadget@gmail.com
In-Reply-To: https://lore.kernel.org/git/pull.1105.v3.git.1641508499.gitgitgadget@gmail.com