Created
April 25, 2018 15:21
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git-neck: a tool for splitting commits
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| #!/bin/sh | |
| # https://opensource.org/licenses/MIT (c) 2018 | |
| # Oren Tirosh <orent@hishome.net> | |
| # | |
| # See and change what your repository looks like from the neck down. | |
| # | |
| # Under git-neck, the HEAD is HEAD^ and worktree is HEAD. | |
| # If you make any changes to the neck, your real HEAD commit is adjusted | |
| # so that its content remains unmodified with the exact same tree hash. | |
| # If you look at it as the difference from its (now modified) parent it | |
| # will appear different. | |
| # | |
| # Examples: | |
| # | |
| # Split a commit: | |
| # git neck status # see contents of commits | |
| # git neck add file # add specific file for new commit | |
| # git neck add -p # add chosen patches to new commit | |
| # git neck commit | |
| # | |
| # The added changes will form a new commit just above your original | |
| # HEAD. You may wish to git commit --amend to update the description | |
| # of HEAD to reflect whatever was removed from it. | |
| # bash only: | |
| trap 'ERRL2=$ERRL1; ERRL1=" at line $LINENO"' DEBUG 2>/dev/null | |
| set -e | |
| trap 'echo Unexpected error$ERRL2' EXIT | |
| exitwith() { | |
| if test "$2" != ""; then echo "${0##*/}: $2" >&2; fi | |
| trap EXIT; exit $1 | |
| } | |
| fail() { | |
| exitwith 1 "$*" | |
| } | |
| REL_GITD="$(git rev-parse --git-dir)" || fail | |
| HEAD_HASH=$(git rev-parse --verify HEAD) || fail | |
| git rev-parse --quiet --verify HEAD^1 >/dev/null || | |
| fail 'Must have at least two commits (HEAD + "NECK")' | |
| ! git rev-parse --quiet --verify HEAD^2 >/dev/null || | |
| fail 'HEAD is a merge commit. We have more than one neck.' | |
| GITD="$(cd "$REL_GITD" && pwd)" | |
| test "$REL_GITD" -ef "$GITD" | |
| NECK_ORIG_HEAD=$(git --git-dir=$GITD/neck/.git rev-parse ORIG_HEAD 2>/dev/null || true) | |
| ngit() { git --git-dir="$NECKD/.git" --work-tree="$NECKD/" "$@"; } | |
| if test "$NECK_ORIG_HEAD" != "$HEAD_HASH"; then | |
| rm -rf "$GITD/neck" "$GITD/neck.tmp" | |
| NECKD="$GITD/neck.tmp" | |
| mkdir -p "$NECKD" | |
| git init --template= -q "$NECKD" | |
| rm -rf "$NECKD/.git/refs" "$NECKD/.git/objects" | |
| ln -s "$GITD/objects" "$NECKD/.git/objects" | |
| ln -s "$GITD/refs" "$NECKD/.git/refs" | |
| ngit update-ref --no-deref HEAD $HEAD_HASH | |
| ngit reset -q HEAD | |
| # Lightweight worktree: only modified files actually checked out | |
| ngit ls-files -z | | |
| ngit update-index --skip-worktree -z --stdin | |
| ngit diff --diff-filter=AMT --name-only --cached HEAD^ -z | | |
| ngit update-index --no-skip-worktree -z --stdin | |
| ngit reset -q --hard HEAD | |
| ngit reset -q HEAD^ | |
| mv "$GITD/neck.tmp" "$GITD/neck" | |
| fi | |
| NECKD="$GITD/neck" | |
| # Run user provided command in temporary repo: | |
| ngit "${@:-status}" || | |
| exitwith $? | |
| NEW_NECK=$(ngit rev-parse HEAD) | |
| ORIG_NECK=$(ngit rev-parse ORIG_HEAD^) | |
| if test "$ORIG_NECK" != "$NEW_NECK"; then | |
| echo "NECK has been modified, updating HEAD" >&2 | |
| HEADCOMMIT=$(git cat-file commit HEAD) | |
| TREELINE="${HEADCOMMIT%%parent*}" | |
| NEWPARENT="parent ${NEW_NECK}" | |
| REMAINDER="${HEADCOMMIT##*parent ????????????????????????????????????????}" | |
| NEWHEAD=$( | |
| echo "$TREELINE$NEWPARENT$REMAINDER" | | |
| git hash-object -t commit -w --stdin | |
| ) | |
| git update-ref -m "git-neck modified" HEAD $NEWHEAD | |
| rm -rf "$NECKD" | |
| fi | |
| exitwith 0 |
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