dep gets confused by internal git environment variables

[sigma]

What version of dep are you using (dep version)?

version 0.4.1

What dep command did you run?

~/tmp/gopath/src/github.com/sdboyer/deptestdos
❯ ls
deptestdos.go  README.md

~/tmp/gopath/src/github.com/sdboyer/deptestdos
❯ export GIT_DIR=`pwd`/.git

❯ dep init -v
Getting direct dependencies...
Checked 1 directories for packages.
Found 1 direct dependencies.
Root project is "github.com/sdboyer/deptestdos"
 1 transitively valid internal packages
 1 external packages imported from 1 projects
(0)   ✓ select (root)
(1)	? attempt github.com/sdboyer/deptest with 1 pkgs; 4 versions to try
(1)	    try github.com/sdboyer/[email protected]
(1)	✗   unable to update checked out version: fatal: reference is not a tree: ff2948a2ac8f538c4ecd55962e919d1e13e74baf
(1)	  : command failed: [git checkout ff2948a2ac8f538c4ecd55962e919d1e13e74baf]: exit status 128
(1)	    try github.com/sdboyer/[email protected]
(1)	✗   unable to update checked out version: fatal: reference is not a tree: 3f4c3bea144e112a69bbe5d8d01c1b09a544253f
(1)	  : command failed: [git checkout 3f4c3bea144e112a69bbe5d8d01c1b09a544253f]: exit status 128
(1)	    try github.com/sdboyer/[email protected]
(1)	✗   unable to update checked out version: fatal: reference is not a tree: ff2948a2ac8f538c4ecd55962e919d1e13e74baf
(1)	  : command failed: [git checkout ff2948a2ac8f538c4ecd55962e919d1e13e74baf]: exit status 128
(1)	    try github.com/sdboyer/deptest@master
(1)	✗   unable to update checked out version: fatal: reference is not a tree: 3f4c3bea144e112a69bbe5d8d01c1b09a544253f
(1)	  : command failed: [git checkout 3f4c3bea144e112a69bbe5d8d01c1b09a544253f]: exit status 128
(1)	  ← no more versions of github.com/sdboyer/deptest to try; begin backtrack
  ✗ solving failed

Solver wall times by segment:
     b-source-exists: 517.514251ms
         b-list-pkgs:  11.015016ms
            new-atom:    166.844µs
             satisfy:    108.747µs
         select-root:     68.589µs
     b-list-versions:     30.368µs
               other:     14.179µs
  b-deduce-proj-root:      3.584µs

  TOTAL: 528.921578ms

init failed: unable to solve the dependency graph: Solving failure: No versions of github.com/sdboyer/deptest met constraints:
	v1.0.0: unable to update checked out version: fatal: reference is not a tree: ff2948a2ac8f538c4ecd55962e919d1e13e74baf
: command failed: [git checkout ff2948a2ac8f538c4ecd55962e919d1e13e74baf]: exit status 128
	v0.8.1: unable to update checked out version: fatal: reference is not a tree: 3f4c3bea144e112a69bbe5d8d01c1b09a544253f
: command failed: [git checkout 3f4c3bea144e112a69bbe5d8d01c1b09a544253f]: exit status 128
	v0.8.0: unable to update checked out version: fatal: reference is not a tree: ff2948a2ac8f538c4ecd55962e919d1e13e74baf
: command failed: [git checkout ff2948a2ac8f538c4ecd55962e919d1e13e74baf]: exit status 128
	master: unable to update checked out version: fatal: reference is not a tree: 3f4c3bea144e112a69bbe5d8d01c1b09a544253f
: command failed: [git checkout 3f4c3bea144e112a69bbe5d8d01c1b09a544253f]: exit status 128

What did you expect to see?

dep init should succeed regardless of how the current git repository is handled (in this case, with an explicit $GIT_DIR).
Note that this is exactly what happens when running something like

git rebase -x ./hack/test.bash origin/master

in order to validate a series of commits.

And since some dep tests actually change the repo "under test", this has unfortunate side-effects (an innocent one being your user.name being changed to "Test author" because of gps/vcs_source_test.go, which is... pretty confusing at first)

What did you see instead?

dep gets very confused, and tries to find dependencies' objects in the main repository's $GIT_DIR, despite the fact that it cloned those dependencies elsewhere.
Note that messing with other GIT_* variables leads to different but related failures, so there's a need to selectively cleanup those.