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fix reversions due to undocumented and buggy git behavior

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* Don't use GIT_PREFIX when GIT_WORK_TREE=. because it seems git
  does not intend GIT_WORK_TREE to be relative to GIT_PREFIX in that
  case, despite GIT_WORK_TREE=.. being relative to GIT_PREFIX.
* Don't use GIT_PREFIX to fix up a relative GIT_DIR, because
  git 2.11 sets GIT_PREFIX set to a path it's not relative to.
  and apparently GIT_DIR is never relative to GIT_PREFIX.

Commit e50ed4ba48 led us down this path
by working around a git bug by relying on the barely documented GIT_PREFIX.

This commit was sponsored by Trenton Cronholm on Patreon.
This commit is contained in:
Joey Hess 2018-09-11 15:53:48 -04:00
parent 30b1e7cb34
commit fdbdf64d87
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4 changed files with 78 additions and 10 deletions
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doc/bugs/v6_-_under_subdir__58___git_add___34__whines__34____44___git_commit___34__blows__34__.mdwn
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@ -47,3 +47,5 @@ git-annex version: 6.20180807+git230-gaa291acfe-1~ndall+1
also happens with 6.20180807-1 but not with 6.20170101-1+deb9u2, so it is a regression
[[!meta author=yoh]]
> [[fixed|done]] --[[Joey]]

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doc/bugs/v6_-_under_subdir__58___git_add___34__whines__34____44___git_commit___34__blows__34__/comment_5_eaafc970cce2c71ce29f136c90e04504._comment Normal file
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@ -0,0 +1,57 @@
[[!comment format=mdwn
username="joey"
subject="""comment 5"""
date="2018-09-11T18:51:07Z"
content="""
Unfortunately git 2.11.0 has the bug that I made git-annex look at
`GIT_PREFIX` to avoid.
root@darkstar:/tmp/repo/foo/bar# git --work-tree=../.. ls-files --modified /tmp/repo/
BASH_EXECUTION_STRING='set | grep GIT_ >&2; pwd >&2; git-annex smudge --clean '\''subdir/file'\'''
GIT_DIR=/tmp/repo/.git
GIT_PREFIX=foo/bar/
GIT_WORK_TREE=../..
/tmp/repo
So, it's not as simple as not looking at `GIT_PREFIX` at all with this
version of git. When `GIT_WORK_TREE` is relative, and `GIT_PREFIX` is set,
it needs to combine them to get the actual path to the work tree.
Perhaps git-annex should only use `GIT_PREFIX`
for fixup of relative `GIT_WORK_TREE`, but not for `GIT_DIR`. I've so
far only seen it be needed for `GIT_WORK_TREE`; I only made it also
be used for `GIT_DIR` out of an assumption git would be consistent in its
bugginess.
Oh hell, here's another way it fails, with git 2.19:
joey@darkstar:/tmp/repo/subdir/foo> git --work-tree=../.. status
BASH_EXECUTION_STRING='set | grep GIT_ >&2; pwd >&2; git-annex smudge --clean '\''subdir/file'\'''
GIT_DIR=/tmp/repo/.git
GIT_EXEC_PATH=/usr/lib/git-core
GIT_MERGE_AUTOEDIT=no
GIT_PAGER=
GIT_PREFIX=subdir/foo/
GIT_WORK_TREE=.
/tmp/repo
git-annex: subdir/file: getFileStatus: does not exist (No such file or directory)
git-annex: smudge: 1 failed
That one does not involve `GIT_DIR`, instead `GIT_WORK_TREE` is not relative to
`GIT_PREFIX` so the workaround that assumes it is breaks. I guess that we
could say that `GIT_DIR` is not relative to some directory in this case,
so the `GIT_PREFIX` is irrelevant.
Kind of feels like git's behavior is so inconsistent and ill-specified
that trying to work around the bugs in it is likely to just be a neverending
source of bugs.
Unfortunately the git devs have so far ignored my bug report despite it
having an easy test case needing nothing more than a simple shell script to
reproduce. And there are plenty of differently broken git versions out there
even if they eventually fix it, so it seems git-annex has to deal with this
mess somehow.
I'm going with not using `GIT_PREFIX` for `GIT_DIR` and not for
`GIT_WORK_TREE=.` and hope that's enough.
"""]]