libgit2 path issues

[pfitzseb]

There are a couple of issues with the current implementation (or the docs) of LibGit2:
Functions like LibGit2.add! take a files argument, which must be (as per here)

• relative to the repos cwd and
• separated by forward slashes.

Since there are no docs for the functions libgit2/index.jl that's a bit of a usability problem which e.g. caused PkgDev.tag to not work on Windows (see JuliaLang/PkgDev.jl#28).

I'd suggest to either

• normalize paths to use forward slashes,
• either error when an absolute path is input or try to resolve it to a path relative to the repos cwd (which should mostly be it's root),
• document the above, and
• test those cases.

or

• document that the path passed to those functions needs to conform to the conditions above and
• throw an error if they don't (instead of silently failing to do anything), and
• test those cases.

I can look into preparing a PR for either of the above if someone decides what to do, but maybe someone more familiar with the codebase would be better suited to do that.

cc @tkelman

[tkelman]

We should attempt to identify which of these limitations come from the c library and which are self inflicted bugs. Command line git lets you use abs paths but errors if you try to add something that's not inaide the current repo, right?

[pfitzseb]

See here and here: libgit2 only allows you to use forward slashes in functions that take git paths (as opposed to filesystem paths), so it's mostly a limitation (or decision, rather) with the c library. I'd argue we should be working around that though.

[tkelman]

Good find. I agree with you and think we should try to do some obvious manipulations before sending to the c library in the bindings instead of needing every user to test and work around the same issues (or all hit this problem if they don't)