From f25af74b44a02aacebe509fc7ecaeb83ffac01f2 Mon Sep 17 00:00:00 2001
From: Daisuke Taniwaki <daisuketaniwaki@gmail.com>
Date: Thu, 13 Jun 2019 13:18:09 +0900
Subject: [PATCH] Show better error message for unexisting commit

---
 pkg/ghost/git/file.go       | 11 +++--------
 pkg/ghost/git/validation.go |  7 ++++++-
 pkg/util/exec.go            | 10 ++++++++++
 3 files changed, 19 insertions(+), 9 deletions(-)

diff --git a/pkg/ghost/git/file.go b/pkg/ghost/git/file.go
index 9ebd3d0..d7d7357 100644
--- a/pkg/ghost/git/file.go
+++ b/pkg/ghost/git/file.go
@@ -18,7 +18,6 @@ import (
 	"fmt"
 	"os"
 	"os/exec"
-	"syscall"
 
 	"github.com/pfnet-research/git-ghost/pkg/util"
 	"github.com/pfnet-research/git-ghost/pkg/util/errors"
@@ -94,13 +93,9 @@ func AppendNonIndexedDiffFiles(dir, filepath string, nonIndexedFilepaths []strin
 		cmd.Stdout = f
 		ggerr := util.JustRunCmd(cmd)
 		if ggerr != nil {
-			if exiterr, ok := ggerr.Cause().(*exec.ExitError); ok {
-				if status, ok := exiterr.Sys().(syscall.WaitStatus); ok {
-					// exit 1 is valid for git diff
-					if status.ExitStatus() == 1 {
-						continue
-					}
-				}
+			if util.GetExitCode(ggerr.Cause()) == 1 {
+				// exit 1 is valid for git diff
+				continue
 			}
 			errs = multierror.Append(errs, ggerr)
 		}
diff --git a/pkg/ghost/git/validation.go b/pkg/ghost/git/validation.go
index ee040fd..c9a0942 100644
--- a/pkg/ghost/git/validation.go
+++ b/pkg/ghost/git/validation.go
@@ -30,7 +30,12 @@ func ValidateGit() errors.GitGhostError {
 
 // ValidateCommittish check committish is valid on dir
 func ValidateCommittish(dir, committish string) errors.GitGhostError {
-	return util.JustRunCmd(
+	output, err := util.JustOutputCmd(
 		exec.Command("git", "-C", dir, "cat-file", "-e", committish),
 	)
+	if err != nil && util.GetExitCode(err.Cause()) == 1 && len(output) == 0 {
+		// exit 1 is for unexisting committish.
+		return errors.Errorf("%s does not exist", committish)
+	}
+	return err
 }
diff --git a/pkg/util/exec.go b/pkg/util/exec.go
index 817acab..399fe20 100644
--- a/pkg/util/exec.go
+++ b/pkg/util/exec.go
@@ -19,6 +19,7 @@ import (
 	"os"
 	"os/exec"
 	"strings"
+	"syscall"
 
 	"github.com/pfnet-research/git-ghost/pkg/util/errors"
 
@@ -62,3 +63,12 @@ func JustRunCmd(cmd *exec.Cmd) errors.GitGhostError {
 	}
 	return nil
 }
+
+func GetExitCode(err error) int {
+	if exiterr, ok := err.(*exec.ExitError); ok {
+		if status, ok := exiterr.Sys().(syscall.WaitStatus); ok {
+			return status.ExitStatus()
+		}
+	}
+	return -1
+}