Use --depth=1 when checking out git repositories

[anguslees]

In most uses of pip's git backend, we don't need the full git history -
only the target head/branch/tag. This change adds --depth=1 to git
fetch and clone commands.

Fixes #2432

[anguslees]

Only "lightly tested" so far. A basic install from git (with and without tag) works, but I haven't tested the various combinations of update() and switch().

NB: (As written) this no longer supports checking out from an arbitrary commit - it needs to be branch name or tag. If this feature is considered critical, then fixing it probably involves recognising the situation and falling back to the previous (full checkout) behaviour :(

[msabramo]

pip installing from an arbitrary commit is very useful

[msabramo]

is that why Travis CI failed?

[blueyed]

pip installing from an arbitrary commit is very useful

Yes, that should not be removed.

@anguslees
Do you see a way to keep this functionality?

It could just use not --depth 1 for this.

See also NixOS's prefetch-git: https://github.com/NixOS/nixpkgs/blob/master/pkgs/build-support/fetchgit/nix-prefetch-git.

[RonnyPfannschmidt]

How does this fare against repos that use setuptools-scm

[blueyed]

Could setuptools-scm use git fetch --unshallow automatically in that case?

[RonnyPfannschmidt]

its tricky to do and error prone, so #d like to avoid it,

[dstufft]

Accidentally closed this, reopening. Sorry!

[BrownTruck]

Hello!

As part of an effort to ease the contribution process and adopt a more standard workflow pip has switched to doing development on the master branch. However, this Pull Request was made against the develop branch so it will need to be resubmitted against master. Unfortunately, this pull request does not cleanly merge against the current master branch.

If you do nothing, this Pull Request will be automatically closed by @BrownTruck since it cannot be merged.

If this pull request is still valid, please rebase it against master (or merge master into it) and resubmit it against the master branch, closing and referencing the original Pull Request.

If you choose to rebase/merge and resubmit this Pull Request, here is an example message that you can copy and paste:

In most uses of pip's git backend, we don't need the full git history -
only the target head/branch/tag.  This change adds --depth=1 to git
fetch and clone commands.

Fixes #2432

---

*This was migrated from pypa/pip#2439 to reparent it to the ``master`` branch. Please see original pull request for any previous discussion.*

[BrownTruck]

This Pull Request was closed because it cannot be automatically reparented to the master branch and it appears to have bit rotted.

Please feel free to re-open it or re-submit it if it is still valid and you have rebased it onto master or merged master into it.