golang_git_exec_fail.go

// EDIT: SOLVED!
// The arguments are supposed to be
// [--no-pager log --all --source --abbrev-commit --grep=Story-Id: 12345]
// not
// [--no-pager log --all --source --abbrev-commit --grep='Story-Id: 12345']
// because then it doesn't find the commits and then output is empty.

// The problem is that my function is returning empty stdout buffer
// even though the output is not empty when I run git from CLI.
//
// OS: Mac OS X 10.7.5
//
// Please note that stdout buffer in this particular Git function is returned empty.
// I changed the function a bit to see what is happening. Originally there was just like
//
//     cmd.Stdout = stdout
//     cmd.Stderr = stderr
//     err = cmd.Run()
//     return
//
// which was not working.
//
// Demo:
//
//    $ test
//    [--no-pager log --all --source --abbrev-commit --grep='Story-Id: 12345']
//    stdout read returned, bytes=0, err=EOF
//
//    $ git --no-pager log --all --source --abbrev-commit --grep='Story-Id: 12345'
//    commit 68f8734	refs/heads/develop
//    Merge: 394ded9 b841987
//    Author: ...
//    Date:   ...
//
//        Finished feature 77965678/test-rb-api
//
//        Story-Id: 12345

func Git(args ...string) (stdout, stderr *bytes.Buffer, err error) {
    stdout = new(bytes.Buffer)
    stderr = new(bytes.Buffer)

    args = append([]string{"--no-pager"}, args...)
    fmt.Println(args)
    cmd := exec.Command("git", args...)
    outPipe, err := cmd.StdoutPipe()
    if err != nil {
        return
    }   
    err = cmd.Start()
    if err != nil {
        return
    }   

    var wg sync.WaitGroup
    wg.Add(1)
    go func() {
        buf := make([]byte, 4096)
        defer wg.Done()
        for {
            n, err := outPipe.Read(buf)
            fmt.Printf("stdout read returned, bytes=%v, err=%v", n, err)
            if err != nil {
                return
            }   
            fmt.Println(buf)
        }   
    }() 
    wg.Wait()

    err = cmd.Wait()
    return
}