From d685e7b4b571c318900ecbc2b5b0fb3d083a259e Mon Sep 17 00:00:00 2001
From: Nick Craig-Wood <nick@craig-wood.com>
Date: Wed, 13 May 2020 12:42:45 +0100
Subject: [PATCH] bin: add check-merged.go to find local branches which might
 have been merged

---
 bin/check-merged.go | 136 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 136 insertions(+)
 create mode 100644 bin/check-merged.go

diff --git a/bin/check-merged.go b/bin/check-merged.go
new file mode 100644
index 000000000..ad68269b7
--- /dev/null
+++ b/bin/check-merged.go
@@ -0,0 +1,136 @@
+// +build ignore
+
+// Attempt to work out if branches have already been merged
+package main
+
+import (
+	"bufio"
+	"errors"
+	"flag"
+	"fmt"
+	"log"
+	"os"
+	"os/exec"
+	"regexp"
+)
+
+var (
+	// Flags
+	master  = flag.String("master", "master", "Branch to work out if merged into")
+	version = "development version" // overridden by goreleaser
+)
+
+func usage() {
+	fmt.Fprintf(os.Stderr, `Usage: %s [options]
+Version: %s
+
+Attempt to work out if in the current git repo branches have been
+merged into master.
+
+Example usage:
+
+    %s
+
+Full options:
+`, os.Args[0], version, os.Args[0])
+	flag.PrintDefaults()
+}
+
+var (
+	printedSep = false
+)
+
+const (
+	sep1 = "============================================================"
+	sep2 = "------------------------------------------------------------"
+)
+
+// Show the diff between two git revisions
+func gitDiffDiff(rev1, rev2 string) {
+	fmt.Printf("Diff of diffs of %q and %q\n", rev1, rev2)
+	cmd := exec.Command("bash", "-c", fmt.Sprintf(`diff <(git show "%s")  <(git show "%s")`, rev1, rev2))
+	out, err := cmd.Output()
+	if err != nil {
+		var exitErr *exec.ExitError
+		if errors.As(err, &exitErr) && exitErr.ExitCode() == 1 {
+			// OK just different
+		} else {
+			log.Fatalf("git diff diff failed: %#v", err)
+		}
+	}
+	_, _ = os.Stdout.Write(out)
+}
+
+var reCommit = regexp.MustCompile(`commit ([0-9a-f]{32,})`)
+
+// Grep the git log for logLine
+func gitLogGrep(branch, rev, logLine string) {
+	cmd := exec.Command("git", "log", "--grep", regexp.QuoteMeta(logLine), *master)
+	out, err := cmd.Output()
+	if err != nil {
+		log.Fatalf("git log grep failed: %v", err)
+	}
+	if len(out) > 0 {
+		if !printedSep {
+			fmt.Println(sep1)
+			printedSep = true
+		}
+		fmt.Printf("Branch: %s - MAY BE MERGED to %s\nLog: %s\n\n", branch, *master, logLine)
+		_, _ = os.Stdout.Write(out)
+		match := reCommit.FindSubmatch(out)
+		if len(match) != 0 {
+			commit := string(match[1])
+			fmt.Println(sep2)
+			gitDiffDiff(rev, commit)
+		}
+		fmt.Println(sep1)
+	}
+}
+
+// * b2-fix-download-url      4209c768a [gone] b2: fix transfers when using download_url
+var reLine = regexp.MustCompile(`^[ *] (\S+)\s+([0-9a-f]+)\s+(?:\[[^]]+\] )?(.*)$`)
+
+// Run git branch -v, parse the output and check it in the log
+func gitBranch() {
+	cmd := exec.Command("git", "branch", "-v")
+	cmd.Stderr = os.Stderr
+	out, err := cmd.StdoutPipe()
+	if err != nil {
+		log.Fatalf("git branch pipe failed: %v", err)
+	}
+	if err := cmd.Start(); err != nil {
+		log.Fatalf("git branch failed: %v", err)
+	}
+	scanner := bufio.NewScanner(out)
+	for scanner.Scan() {
+		line := scanner.Text()
+		match := reLine.FindStringSubmatch(line)
+		if len(match) != 4 {
+			log.Printf("Invalid line %q", line)
+			continue
+		}
+		branch, rev, logLine := match[1], match[2], match[3]
+		if branch == *master {
+			continue
+		}
+		//fmt.Printf("branch = %q, rev = %q, logLine = %q\n", branch, rev, logLine)
+		gitLogGrep(branch, rev, logLine)
+	}
+	if err := scanner.Err(); err != nil {
+		log.Fatalf("failed reading git branch: %v", err)
+	}
+	if err := cmd.Wait(); err != nil {
+		log.Fatalf("git branch wait failed: %v", err)
+	}
+}
+
+func main() {
+	flag.Usage = usage
+	flag.Parse()
+	args := flag.Args()
+	if len(args) != 0 {
+		usage()
+		log.Fatal("Wrong number of arguments")
+	}
+	gitBranch()
+}