Continuous deployment and difference in hashes between fetcher functions

[pikajude]

I have a darcs repo for my personal website. I have a continuous build running for it in Hydra. Unfortunately, since I use src = ./. instead of using a tarball and SHA (see: http://hub.darcs.net/joelteon/joelt.io/browse/default.nix), I can't use a cached Hydra build. On my machine, the store import of the source tree is (for example) /nix/store/1mcp51riccrkfrhb5jlbx3nzcrw16l5w-joelt.io. An identical copy of the source tree in Hydra would be something like /nix/store/kg69sya7fny2m5bp6r9i40q3xb6slp75-export, because even if the directory contents are identical, the directory name is taken into account.

Even if I patch Hydra to clone into a temporary directory with the correct repository name, Hydra imports the existing import into the store again for the build, so the actual source tree during build is /nix/store/g05db63rfxy3n0z9nwhjijfdvficakq4-1mcp51riccrkfrhb5jlbx3nzcrw16l5w-joelt.io.

I know that one workaround would be to use a source tarball, but that's an extra step and requires that I have the source somewhere and keep it updated, which really isn't ideal for a continuous deployment situation.

Is this a problem that can be solved?

[domenkozar]

I duplicated this in NixOS/nix#904

[expipiplus1]

Is the directory name the only other changes to the hash that hydra is making?

I have foo/bar/default.nix in my repo, where default.nix has the line src = ./.. Hydra and my local machine seem to put the source in /nix/store/1mcp51riccrkfrhb5jlbx3nzcrw16l51-bar and /nix/store/kg69sya7fny2m5bp6r9i40q3xb6slp71-bar respectively. These paths were found by examining the value for "src" in the derivations being built.

[expipiplus1]

Ah, I cant seem to find the issue number, but the source coming from a subdirectory does indeed work. The problem was that hydra was stripping .gitignore away from the subdirectory.

[Ericson2314]

Can't the name of the current directory also not affect the hash of ./.? I see no purpose for that. (Granted, this is a nix not hydra question.)

[domenkozar]

That would be ideal, but then it's possible to have:

/nix/store/kg69sya7fny2m5bp6r9i40q3xb6slp71-bar
/nix/store/kg69sya7fny2m5bp6r9i40q3xb6slp71-foo

Which in practice wouldn't happen often, but would that be an issue? This would be a backwards incompatible change for Nix that Eelco wouldn't be willing to do IMO.