Fixing source/path and GIT_* issues

[groutr]

The overarching goal of this PR is to fix issues with source/path (#783).

I uncovered a subtle issue with the Metadata.get_value() method not behaving as expected (see 3bd490d)

[stuarteberg]

BTW, #803 addresses some related (but different) issues to the ones you're addressing here.

[groutr]

@stuarteberg Could you explain to me what you expect get_git_build_info(src_dir, git_url, None) to mean?

[stuarteberg]

Could you explain to me what you expect get_git_build_info(src_dir, git_url, None) to mean?

I'm thinking about this line:

d.update(**get_git_build_info(d['SRC_DIR'],
                              git_url,
                              m.get_value('source/git_rev')))

If third argument evaluates to None, then get_git_build_info() needs to replace it with a suitable default value. (The original default was 'master', but a better default would be 'HEAD', as proposed in #803.)

[groutr]

m.get_value('source/git_rev') won't evaluate to None. By default it will evaluate to text_type()
The only way I can see a None being passed in is if it was explicitly passed in.

[stuarteberg]

By default it will evaluate to text_type()

Ah, okay. Still, for the purposes of this discussion, None and '' have the same meaning.

[groutr]

Oh, that third option is supposed to be m.get_value('source/git_rev', 'HEAD'). That's why I fixed the get_value() function.

[stuarteberg]

Sure, that works, too.

[stuarteberg]

BTW, there are likely to be a couple tiny conflicts between this PR and #803. Not sure if you want to merge that first and rebase this or vice-versa.

[groutr]

Probably best to merge #803 first.

[stuarteberg]

Also, #790 touches the same function. Might want to look there, too.

[jakirkham]

This probably needs its build restarted, but I don't know if it is worth worrying about at this point.

[ccordoba12]

@kalefranz, could you review this one? I'm sure the lack of GIT_* variables is breaking a lot of people's workflows (including ours in Navigator).

[msarahan]

LGTM. Merging. Thanks @groutr @stuarteberg @jakirkham

[stuarteberg]

I like these changes, @groutr. Nicely done. Thanks for merging, @msarahan.