mr_create: Check for zero commits in a Merge Request

It is possible to open up a Merge Request with zero commits by pushing a
branch with no changes and then executing 'lab mr create'.

lab should abort the creation of an MR in this case.

Check the number of commits in the remote branch, and if it is zero, abort
the creation of the Merge Request.

Signed-off-by: Prarit Bhargava <[email protected]>

cmd/mr_create.go

@@ -286,12 +286,17 @@ func mrText(base, head, sourceRemote, targetRemote string, coverLetterFormat boo
 	)
 	remoteBase := fmt.Sprintf("%s/%s", targetRemote, base)
 	commitMsg = ""
-	if git.NumberCommits(remoteBase, head) == 1 {
+
+	numCommits := git.NumberCommits(remoteBase, head)
+	if numCommits == 1 {
 		commitMsg, err = git.LastCommitMessage()
 		if err != nil {
 			return "", err
 		}
 	}
+	if numCommits == 0 {
+		return "", errors.New("Aborting: Resulting Merge Request would have had 0 commits.")
+	}
 
 	const tmpl = `{{if .InitMsg}}{{.InitMsg}}{{end}}
 
@@ -307,10 +312,11 @@ func mrText(base, head, sourceRemote, targetRemote string, coverLetterFormat boo
 
 	mrTmpl := lab.LoadGitLabTmpl(lab.TmplMR)
 
-	commitLogs, numCommits, err := git.Log(remoteBase, head)
+	commitLogs, err := git.Log(remoteBase, head)
 	if err != nil {
 		return "", err
 	}
+
 	commitLogs = strings.TrimSpace(commitLogs)
 	commentChar := git.CommentChar()
 

internal/git/git.go

@@ -8,7 +8,6 @@ import (
 	"os/exec"
 	"path/filepath"
 	"regexp"
-	"strconv"
 	"strings"
 	"time"
 
@@ -117,7 +116,7 @@ func LastCommitMessage() (string, error) {
 }
 
 // Log produces a formatted gitlog between 2 git shas
-func Log(sha1, sha2 string) (string, int, error) {
+func Log(sha1, sha2 string) (string, error) {
 	cmd := New("-c", "log.showSignature=false",
 		"log",
 		"--no-color",
@@ -127,28 +126,17 @@ func Log(sha1, sha2 string) (string, int, error) {
 	cmd.Stdout = nil
 	outputs, err := cmd.Output()
 	if err != nil {
-		return "", 0, errors.Errorf("Can't load git log %s..%s", sha1, sha2)
+		return "", errors.Errorf("Can't load git log %s..%s", sha1, sha2)
 	}
 
 	diffCmd := New("diff", "--stat", sha1)
 	diffCmd.Stdout = nil
 	diffOutput, err := diffCmd.Output()
 	if err != nil {
-		return "", 0, errors.Errorf("Can't load diffstat")
+		return "", errors.Errorf("Can't load diffstat")
 	}
 
-	numCommitsCmd := New("rev-list", "--count", fmt.Sprintf("%s...%s", sha1, sha2))
-	numCommitsCmd.Stdout = nil
-	numCommitsString, err := numCommitsCmd.Output()
-	if err != nil {
-		return "", 0, errors.Errorf("Can't determine number of commits")
-	}
-	numCommits, err := strconv.Atoi(strings.TrimSpace(string(numCommitsString)))
-	if err != nil {
-		return "", 0, errors.Errorf("Can't determine number of commits(%s)", numCommitsString)
-	}
-
-	return string(outputs) + string(diffOutput), numCommits, nil
+	return string(outputs) + string(diffOutput), nil
 }
 
 // CurrentBranch returns the currently checked out branch

internal/git/git_test.go

@@ -73,10 +73,11 @@ func TestLastCommitMessage(t *testing.T) {
 }
 
 func TestLog(t *testing.T) {
-	log, count, err := Log("HEAD~1", "HEAD")
+	log, err := Log("HEAD~1", "HEAD")
 	if err != nil {
 		t.Fatal(err)
 	}
+	count := NumberCommits("HEAD~1", "HEAD")
 	expectedSHA := "09b519c"
 	expectedAuthor := "Zaq? Wiedmann"
 	expectedMessage := "(ci) jobs with interleaved sleeps and prints"