Buffer read change in Go 1.7 breaks readObjectFile()

[snicol]

I found that after upgrading to Go 1.7, repo.GetCommitOfBranch(branch) started returning an EOF and not the commit sha1 that I expected.

https://github.com/gogits/git/blob/564c5fe86bbef8589421582b69657cc08c4c85fb/repo_utils.go#L306

I dug in and found that simply removing the error check fixes this, which matches up with the release notes below.

In previous releases of Go, if Reader's Read method were asked for zero bytes with no data remaining, it would return a count of 0 and no error. Now it returns a count of 0 and the error io.EOF

[lemmi]

this should at least check for the number of bytes read or use io.ReadFull or something. leaving out the check is probably not the right thing to do.

[snicol]

Definitely, I only removed the check to see if that change was the cause. I will submit a PR with the >0 bytes check 😊