bin/git-cut-branch

   1 #!/bin/sh
   2 #/ Usage: git-cut-branch <name>
   3 #/ Create a new branch named <name> pointed at HEAD and reset the current branch
   4 #/ to the head of its tracking branch. This is useful when working on master and
   5 #/ you realize you should be on a topic branch.
   6 set -e
   7
   8 # bail out with message to stderr and exit status 1
   9 die() {
  10     echo "$(basename $0):" "$@" 1>&2
  11     exit 1
  12 }
  13
  14 # write a short sha for the given sha
  15 shortsha() {
  16     echo "$1" |cut -c1-7
  17 }
  18
  19 # show usage
  20 [ -z "$1" -o "$1" = "--help" ] && {
  21     grep '^#/' "$0" |cut -c4-
  22     exit 2
  23 }
  24
  25 # first argument is the new branch name
  26 branch="$1"
  27
  28 # get the current branch for HEAD in refs/heads/<branch> form
  29 ref=$(git symbolic-ref -q HEAD)
  30 sha=$(git rev-parse HEAD)
  31 [ -n "$ref" ] ||
  32 die "you're not on a branch"
  33
  34 # just the branch name please
  35 current=$(echo "$ref" |sed 's@^refs/heads/@@')
  36 [ -n "$current" ] ||
  37 die "you're in a weird place; get on a local branch"
  38
  39 # figure out what branch we're currently tracking
  40 remote=$(git config --get "branch.$current.remote" || true)
  41 merge=$(git config --get "branch.$current.merge" | sed 's@refs/heads/@@')
  42
  43 # build up a sane <remote>/<branch> name
  44 if [ -n "$remote" -a -n "$merge" ]
  45 then tracking="$remote/$merge"
  46 elif [ -n "$merge" ]
  47 then tracking="$merge"
  48 else die "$current is not tracking anything"
  49 fi
  50
  51 # make sure there's no changes before we reset hard
  52 if ! git diff-index --quiet --cached HEAD || ! git diff-files --quiet
  53 then die "cannot cut branch with changes to index or working directory"
  54 fi
  55
  56 # reset the current branch to its tracking branch, create the new branch also
  57 # tracking the original branch, and switch to it.
  58 git branch "$branch"
  59 git reset -q --hard "$tracking"
  60 git checkout -q "$branch"
  61 git branch --set-upstream "$branch" "$tracking"
  62 git reset -q --hard "$sha"
  63 echo "[$(shortsha "$sha")...$(shortsha $(git rev-parse $tracking))] $current"
  64 echo "[0000000...$(shortsha $(git rev-parse HEAD))] $branch"