From e97dabe6b0211915f6853bfeaa71b9d34dfe6667 Mon Sep 17 00:00:00 2001
From: Jeremy Stribling <strib@alum.mit.edu>
Date: Wed, 2 Aug 2017 14:52:46 -0700
Subject: [PATCH] plumbing: use --exec-path to find pack executables

Suggested by smola.

Issue: #527
---
 plumbing/transport/file/client.go             | 48 ++++++++++++++++++-
 plumbing/transport/file/client_cmd_unix.go    | 18 -------
 plumbing/transport/file/client_cmd_windows.go | 29 -----------
 3 files changed, 47 insertions(+), 48 deletions(-)
 delete mode 100644 plumbing/transport/file/client_cmd_unix.go
 delete mode 100644 plumbing/transport/file/client_cmd_windows.go

diff --git a/plumbing/transport/file/client.go b/plumbing/transport/file/client.go
index 3d058aa0c..f093a7b94 100644
--- a/plumbing/transport/file/client.go
+++ b/plumbing/transport/file/client.go
@@ -2,9 +2,13 @@
 package file
 
 import (
+	"bufio"
+	"errors"
 	"io"
 	"os"
 	"os/exec"
+	"path/filepath"
+	"strings"
 
 	"gopkg.in/src-d/go-git.v4/plumbing/transport"
 	"gopkg.in/src-d/go-git.v4/plumbing/transport/internal/common"
@@ -30,6 +34,38 @@ func NewClient(uploadPackBin, receivePackBin string) transport.Transport {
 	})
 }
 
+func prefixExecPath(cmd string) (string, error) {
+	// Use `git --exec-path` to find the exec path.
+	execCmd := exec.Command("git", "--exec-path")
+
+	stdout, err := execCmd.StdoutPipe()
+	if err != nil {
+		return "", err
+	}
+	stdoutBuf := bufio.NewReader(stdout)
+
+	err = execCmd.Start()
+	if err != nil {
+		return "", err
+	}
+
+	execPathBytes, isPrefix, err := stdoutBuf.ReadLine()
+	if err != nil {
+		return "", err
+	}
+	if isPrefix {
+		return "", errors.New("Couldn't read exec-path line all at once")
+	}
+
+	err = execCmd.Wait()
+	if err != nil {
+		return "", err
+	}
+	execPath := string(execPathBytes)
+	execPath = strings.TrimSpace(execPath)
+	return filepath.Join(execPath, cmd), nil
+}
+
 func (r *runner) Command(cmd string, ep transport.Endpoint, auth transport.AuthMethod,
 ) (common.Command, error) {
 
@@ -40,7 +76,17 @@ func (r *runner) Command(cmd string, ep transport.Endpoint, auth transport.AuthM
 		cmd = r.ReceivePackBin
 	}
 
-	return makeCommand(cmd, ep)
+	_, err := exec.LookPath(cmd)
+	if err != nil {
+		if e, ok := err.(*exec.Error); ok && e.Err == exec.ErrNotFound {
+			cmd, err = prefixExecPath(cmd)
+			if err != nil {
+				return nil, err
+			}
+		}
+	}
+
+	return &command{cmd: exec.Command(cmd, ep.Path())}, nil
 }
 
 type command struct {
diff --git a/plumbing/transport/file/client_cmd_unix.go b/plumbing/transport/file/client_cmd_unix.go
deleted file mode 100644
index abe3e9ffd..000000000
--- a/plumbing/transport/file/client_cmd_unix.go
+++ /dev/null
@@ -1,18 +0,0 @@
-// +build !windows
-
-package file
-
-import (
-	"os/exec"
-
-	"gopkg.in/src-d/go-git.v4/plumbing/transport"
-	"gopkg.in/src-d/go-git.v4/plumbing/transport/internal/common"
-)
-
-func makeCommand(cmd string, ep transport.Endpoint) (common.Command, error) {
-	if _, err := exec.LookPath(cmd); err != nil {
-		return nil, err
-	}
-
-	return &command{cmd: exec.Command(cmd, ep.Path())}, nil
-}
diff --git a/plumbing/transport/file/client_cmd_windows.go b/plumbing/transport/file/client_cmd_windows.go
deleted file mode 100644
index b58bbb2da..000000000
--- a/plumbing/transport/file/client_cmd_windows.go
+++ /dev/null
@@ -1,29 +0,0 @@
-// +build windows
-
-package file
-
-import (
-	"os/exec"
-	"strings"
-
-	"gopkg.in/src-d/go-git.v4/plumbing/transport"
-	"gopkg.in/src-d/go-git.v4/plumbing/transport/internal/common"
-)
-
-// In the default Windows git install, there is no separate
-// git-upload-pack or git-receive-pack binaries; we must use "git
-// upload-pack" and "git receive-pack" instead.
-func makeCommand(cmd string, ep transport.Endpoint) (common.Command, error) {
-	var subcommands []string
-	if strings.HasPrefix(cmd, "git-") {
-		subcommands = strings.SplitN(cmd, "-", 2)
-		cmd = subcommands[0]
-	}
-
-	if _, err := exec.LookPath(cmd); err != nil {
-		return nil, err
-	}
-
-	return &command{cmd: exec.Command(
-		cmd, append(subcommands[1:], ep.Path())...)}, nil
-}