builtins.fetchGit improvement with unclean repo's

[cleverca22]

nix/src/libexpr/primops/fetchGit.cc

Lines 38 to 45 in e89d02b

	try {
	runProgram("git", true, { "-C", uri, "diff-index", "--quiet", "HEAD", "--" });
	} catch (ExecError e) {
	if (!WIFEXITED(e.status) || WEXITSTATUS(e.status) != 1) throw;
	clean = false;
	}
	if (!clean) {

currently, if a repo is not clean, fetchGit returns all 0's for the revision

my proposal, is that it return the current revision, and boolean flag to indicate that it has been modified, so you at least know what the starting point is, rather then having no clue what the version is

for example:

nix-repl> builtins.fetchGit ./.
{ outPath = "/nix/store/311jjk1bcwqzb0fi7xial2lrz6wr14s3-source"; rev = "72cab907664d22b4dea0d1590f881d6cd0bbf36f"; revCount = 16; shortRev = "72cab90"; modified = true; }

[grahamc]

or perhaps using <commit>-dirty, like how git describe --dirty will

[kaii-zen]

In one of the projects I work on I actually id the "dirt" as it helps when I want to deploy things for testing before actually committing. The easiest way I found for doing that is to just use GIT_INDEX_FILE to create an index in a temp file and then hashing the output of git diff:

export GIT_INDEX_FILE=$(mktemp -d)/idx
git add --all
git --no-pager diff --no-color HEAD | git hash-object --stdin
rm $GIT_INDEX_FILE

Here's a fairly more robust (albeit still contrived) version https://gist.github.com/kreisys/2fd049bd8c6f40a412067bead6184923
if you save it to /usr/local/bin/git-dirt then you can run git dirt to get the dirt hash or git dirt -s for the short version.

[stale]

I marked this as stale due to inactivity. → More info

[mkohler]

It looks to me like a feature very similar to this was implemented in #5385 and merged to master on June 24, 2023.

[roberth]

This has been implemented in #5385. Thanks @mkohler.

nix-repl> builtins.fetchGit ./.
warning: Git tree '/home/user/src/nix' is dirty
{
  dirtyRev = "644ebaab5f96089bc3a8fd3873e8e7f2131a9074-dirty"; 
  dirtyShortRev = "644ebaab5-dirty"; 
  lastModified = 1696604297; 
  lastModifiedDate = "20231006145817"; 
  narHash = "sha256-xxDbF1XGBSxgFekFjYVVwhwFe2bMaKyoeHgaj2btYH8="; 
  outPath = "/nix/store/1r3n5s4pv4jcpxiw6akjqwc0yz8ki3ah-source"; 
  rev = "0000000000000000000000000000000000000000"; 
  revCount = 0; 
  shortRev = "0000000"; 
  submodules = false;
}