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git fetcher: invoke diff instead of diff-index

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diff-index operates on the view that git has of the working tree,
which might be outdated. The higher-level diff command does this
automatically. This change also adds handling for submodules.

fixes #4140

Alternative fixes would be invoking update-index before diff-index or
matching more closely what require_clean_work_tree from git-sh-setup.sh
does, but both those options make it more difficult to reason about
correctness.
This commit is contained in:
Martin Schwaighofer 2021-12-13 21:31:20 +01:00
parent 0bfa0cdea1
commit c7e527b82b
2 changed files with 17 additions and 2 deletions
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12
src/libfetchers/git.cc
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@ -235,7 +235,17 @@ struct GitInputScheme : InputScheme
try {
if (hasHead) {
runProgram("git", true, { "-C", actualUrl, "diff-index", "--quiet", "HEAD", "--" });
// Using git diff is preferrable over lower-level operations here,
// because its conceptually simpler and we only need the exit code anyways.
auto gitDiffOpts = Strings({ "-C", actualUrl, "diff", "HEAD", "--quiet"});
if (!submodules) {
// Changes in submodules should only make the tree dirty
// when those submodules will be copied as well.
gitDiffOpts.emplace_back("--ignore-submodules");
}
gitDiffOpts.emplace_back("--");
runProgram("git", true, gitDiffOpts);
clean = true;
}
} catch (ExecError & e) {

7
tests/fetchGit.sh
View file

@ -11,7 +11,7 @@ repo=$TEST_ROOT/git
export _NIX_FORCE_HTTP=1
rm -rf $repo ${repo}-tmp $TEST_HOME/.cache/nix $TEST_ROOT/worktree $TEST_ROOT/shallow
rm -rf $repo ${repo}-tmp $TEST_HOME/.cache/nix $TEST_ROOT/worktree $TEST_ROOT/shallow $TEST_ROOT/minimal
git init $repo
git -C $repo config user.email "foobar@example.com"
@ -147,8 +147,13 @@ path3=$(nix eval --impure --raw --expr "(builtins.fetchGit $repo).outPath")
# (check dirty-tree handling was used)
[[ $(nix eval --impure --raw --expr "(builtins.fetchGit $repo).rev") = 0000000000000000000000000000000000000000 ]]
[[ $(nix eval --impure --raw --expr "(builtins.fetchGit $repo).shortRev") = 0000000 ]]
# Making a dirty tree clean again and fetching it should
# record correct revision information. See: #4140
echo world > $repo/hello
[[ $(nix eval --impure --raw --expr "(builtins.fetchGit $repo).rev") = $rev2 ]]
# Committing shouldn't change store path, or switch to using 'master'
echo dev > $repo/hello
git -C $repo commit -m 'Bla5' -a
path4=$(nix eval --impure --raw --expr "(builtins.fetchGit $repo).outPath")
[[ $(cat $path4/hello) = dev ]]