Windows support

[alexsaveliev]

• replaced "git rev-parse SPEC^{commit}" with short-hand "git rev-parse SPEC^0" because {} has a special meaning in Windows
• git client expects path arguments to use slashes, so forcing them
• ssh expects path to key file (-i KEY) to use slashes (checked with Cygwin's git and MSYS's git)
• forcing using slashes instead of OS-specific file separator
• making OS-specific GIT_SSH and GIT_ASKPASS helpers (bat files on Windows vs shell scripts on Unix)
• fixed some unit tests (actually everything but "native git" work now on Windows)
• os.Chmod is platform-independent while os.File.Chmod is not implemented on Windows
• On Windows, commit hash may differ when there are symlinks made by different tool (Cygwin/Msys/...) thus computing proper hash before test (affects unit tests)
• code refactoring: extracted method to write a file and set permissions after
• fixed "native hg" stat() method on Windows

TODO list:

• is there a easy way to make "native git" compile on Windows?
• enhance TestRepository_FileSystem_Symlinks test on Windows - I made some pieces to execute on Unix/Darwin only

[dmitshur]

replaced "git rev-parse SPEC^{commit}" with short-hand "git rev-parse SPEC^0" because {} has a special meaning in Windows

I wanted to verify that doing this wouldn't cause a regression for #37, and it appears to be okay.

[alexsaveliev]

I wanted to verify that doing this wouldn't cause a regression for #37 https://github.com/sourcegraph/go-vcs/issues/37, but it appears to be okay.

https://git-scm.com/docs/git-rev-parse states

...As a special rule, ^0 means the commit itself and is used when

is the object name of a tag object that refers to a commit object.... so ^0 is identical to ^{commit}.

[dmitshur]

https://git-scm.com/docs/git-rev-parse states

...As a special rule, ^0 means the commit itself and is used when

is the object name of a tag object that refers to a commit object.... so ^0 is identical to ^{commit}.

Great, it's good that the docs confirm it too.

[beyang]

Other than comments, LGTM. Why is Travis failing?

[dmitshur]

Travis is failing on Go 1.2 and 1.3, but passing on 1.4 and tip. It's because the golang.org/x/crypto/ssh package uses crypto.Signer which is available on Go 1.4 and later.

I think we should drop Go 1.2 and 1.3, and use 1.4, 1.5, and tip. 1.3 is more than 1 major version behind current release.

[beyang]

yeah, let's go ahead and drop everything below 1.4. @alexsaveliev can you update the travis.yml?

[alexsaveliev]

Updated travis.yml to include only Go 1.4+