[PATCH v2 4/5] update-index doc: note a fixed bug in the untracked cache

From: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Date: Jan 3, 2018, 20:49 UTC
Message-ID: <20180103204928.3769-5-avarab@gmail.com>
In-Reply-To: <20180103204928.3769-1-avarab@gmail.com>

Document the bug tested for in my "status: add a failing test showing a core.untrackedCache bug" and fixed in Duy's "dir.c: fix missing dir invalidation in untracked code".

Since this is very likely something others will encounter in the future on older versions, and it's not obvious how to fix it let's document both that it exists, and how to "fix" it with a one-off command.

As noted in that commit, even though this bug gets the untracked cache into a bad state, we have not yet found a case where this is user visible, and thus it makes sense for these docs to focus on the symlink case only.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
---
 Documentation/git-update-index.txt | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/Documentation/git-update-index.txt b/Documentation/git-update-index.txt
index bdb0342593..128e0c671f 100644
--- a/Documentation/git-update-index.txt
+++ b/Documentation/git-update-index.txt
@@ -464,6 +464,22 @@ command reads the index; while when `--[no-|force-]untracked-cache`
 are used, the untracked cache is immediately added to or removed from
 the index.
 
+Before 2.16, the untracked cache had a bug where replacing a directory
+with a symlink to another directory could cause it to incorrectly show
+files tracked by git as untracked. See the "status: add a failing test
+showing a core.untrackedCache bug" commit to git.git. A workaround for
+that was (and this might work for other undiscoverd bugs in the
+future):
+
+----------------
+$ git -c core.untrackedCache=false status
+----------------
+
+This bug has also been shown to affect non-symlink cases of replacing
+a directory with a file when it comes to the internal structures of
+the untracked cache, but no case has been found where this resulted in
+wrong "git status" output.
+
 File System Monitor
 -------------------

-- 
2.15.1.424.g9478a66081