Revert r305598, "utils: Add a git-r utility for mapping svn revisions to git revisions in the monorepo."

$ git revert `git r 305598`

We need to decide whether we want development tools to be written in
Go first.

llvm-svn: 305741

utils/git-svn/git-r/git-r.go

@@ -1,169 +0,0 @@
-//===- git-r.go - svn revisions to git revisions --------------------------===//
-//
-//                     The LLVM Compiler Infrastructure
-//
-// This file is distributed under the University of Illinois Open Source
-// License. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-//
-// This is a small program for mapping svn revisions to git revisions in the
-// monorepo.
-//
-// To set up:
-// 1) http://llvm.org/docs/GettingStarted.html#for-developers-to-work-with-a-git-monorepo
-//    and make sure to follow the instructions for fetching commit notes.
-// 2) go build
-// 3) cp git-r ~/bin
-//
-// To use:
-// $ git r 1
-// 09c4b68e68c4fcff64b00e1ac077c4f4a524cbcc
-//
-//===----------------------------------------------------------------------===//
-
-package main
-
-import (
-	"bufio"
-	"bytes"
-	"encoding/gob"
-	"fmt"
-	"log"
-	"os"
-	"os/exec"
-	"strconv"
-	"strings"
-)
-
-func git(args ...string) (*bytes.Buffer, error) {
-	cmd := exec.Command("git", args...)
-
-	var b bytes.Buffer
-	cmd.Stdout = &b
-	err := cmd.Run()
-
-	return &b, err
-}
-
-func mkrevmap() []string {
-	revs, err := git("grep", "git-svn-rev", "refs/notes/commits")
-	if err != nil {
-		panic(err)
-	}
-
-	var revmap []string
-
-	scanner := bufio.NewScanner(revs)
-	for scanner.Scan() {
-		// refs/notes/commits:00/0b/d4acb454290301c140a1d9c4f7a45aa2fa9c:git-svn-rev: 37235
-
-		bits := strings.Split(scanner.Text(), ":")
-		gitrev := strings.Replace(bits[1], "/", "", -1)
-		svnrev := bits[3][1:]
-
-		svnrevn, err := strconv.Atoi(svnrev)
-		if err != nil {
-			panic(err)
-		}
-
-		if svnrevn >= len(revmap) {
-			newrevmap := make([]string, svnrevn+1)
-			copy(newrevmap, revmap)
-			revmap = newrevmap
-		}
-		revmap[svnrevn] = gitrev
-	}
-
-	return revmap
-}
-
-type revmap struct {
-	Noterev string
-	Revs    []string
-}
-
-func writerevmap(path string, rmap *revmap, svnrev int) {
-	noterevbuf, err := git("rev-parse", "refs/notes/commits")
-	if err != nil {
-		fmt.Fprintf(os.Stderr, "%s: could not find refs/notes/commits, see instructions:\n", os.Args[0])
-		fmt.Fprintln(os.Stderr, "http://llvm.org/docs/GettingStarted.html#for-developers-to-work-with-a-git-monorepo")
-		os.Exit(1)
-	}
-	noterev := noterevbuf.String()
-	noterev = noterev[:len(noterev)-1]
-
-	if rmap == nil || rmap.Noterev != noterev {
-		var newrmap revmap
-		newrmap.Revs = mkrevmap()
-		newrmap.Noterev = noterev
-
-		f, err := os.Create(path)
-		if err != nil {
-			panic(err)
-		}
-
-		enc := gob.NewEncoder(f)
-		err = enc.Encode(newrmap)
-		if err != nil {
-			os.Remove(path)
-			panic(err)
-		}
-
-		rmap = &newrmap
-	}
-
-	if svnrev >= len(rmap.Revs) || rmap.Revs[svnrev] == "" {
-		fmt.Fprintf(os.Stderr, "%s: %d: unknown revision\n", os.Args[0], svnrev)
-		os.Exit(1)
-	}
-
-	fmt.Println(rmap.Revs[svnrev])
-}
-
-func main() {
-	if len(os.Args) != 2 {
-		fmt.Fprintf(os.Stderr, "%s: expected a single argument\n", os.Args[0])
-		os.Exit(1)
-	}
-	svnrev, err := strconv.Atoi(os.Args[1])
-	if err != nil {
-		fmt.Fprintf(os.Stderr, "%s: %s: expected an integer argument\n", os.Args[0], os.Args[1])
-		os.Exit(1)
-	}
-
-	gitdirbuf, err := git("rev-parse", "--git-common-dir")
-	if err != nil {
-		fmt.Fprintf(os.Stderr, "%s: not in a git repository\n", os.Args[0])
-		os.Exit(1)
-	}
-
-	gitdir := gitdirbuf.String()
-	gitdir = gitdir[:len(gitdir)-1]
-	err = os.Chdir(gitdir)
-	if err != nil {
-		panic(err)
-	}
-
-	mappath := "git-svn-revmap-cache"
-	f, err := os.Open(mappath)
-	if err != nil {
-		writerevmap(mappath, nil, svnrev)
-		return
-	}
-
-	dec := gob.NewDecoder(f)
-	var rmap revmap
-	err = dec.Decode(&rmap)
-	if err != nil {
-		writerevmap(mappath, nil, svnrev)
-		return
-	}
-
-	if svnrev < len(rmap.Revs) && rmap.Revs[svnrev] != "" {
-		fmt.Println(rmap.Revs[svnrev])
-		return
-	}
-
-	writerevmap(mappath, &rmap, svnrev)
-}