save misses dependencies under build constraints

[kr]

If a dependency is under build constraints that are not locally satisfied (for example, a foo_windows.go file on a unix machine), then godep save won't pick it up.

[kr]

The current approach is to duplicate the go tool's logic for scanning packages (and therefore stop calling the go tool). But that's a substantial amount of new code for godep (about 1000 lines), so I just asked about a couple of possible alternatives on golang-nuts:

https://groups.google.com/d/msg/golang-nuts/4Bgl5DcPuBw/UjGonF4nOpAJ

[nielsdraaisma]

I ran into this issue this week and worked around our problem by adding a '-tags foo' option to the save command, which get's passed along into "go list" command.

If this is an acceptable workaround that helps others i'm happy to bind it up and stick it in a pull request.

[jzelinskie]

I believe that I created a duplicate issue at #161. However, some new information has come to light: if a library is using the ! operator in a build line (i.e. // +build !linux), even the -tags parameter on go list won't help.

I'm thinking that getting UserAllFiles exposed is the proper solution.

[freeformz]

Closing in favor of #271.