git-reapply-patch

#!/bin/sh
# git-reapply-patch (part of ossobv/vcutil) // wdoekes/2019 // Public Domain
#
# Apply/patch a regular (--format=medium) git-show formatted patch,
# using the Author, Date and Message found therein, adding a cherry-pick
# message.
#
# Basic usage:
#
#     # If you have a changeset...
#     git show 2ddef2d7 >cherry-picked.patch  # fetch some commit
#
#     # ... that you want committed/cherry-picked somewhere.
#     git checkout -b other-branch 2ddef2d7^
#
#     # Then you take the git-show output, and apply it, with an
#     # optional extra message:
#     git-reapply-patch cherry-picked.patch "(this is an example)"
#
# This would create a changeset with the Date, Author and Message from
# the patch file, and the following lines appended to the commit mesage:
#
#     (git-reapply-patch cherry-pick 2ddef2d7)
#     (this is an example)
#
# A more advanced use case is when you want to rewrite some history and
# you have an ordered list of git-show formatted patches that you want
# to re-apply.
#
#     for patch_file in *.patch; do
#         git-reapply-path $patch_file "(The Big Rewrite)" || break
#         mv $patch_file ${patch_file}.done
#     done
#
# If you run into conflicts, you can fix them manually by staging the
# area appropriately, and then use "--only-commit". This will skip the
# apply step, and only do the commit step with the Date, Author and
# (amended) Message.
#
#     git-reapply-patch $patch_file "(The Big Rewrite)" --only-commit
#     mv $patch_file ${patch_file}.done
#
patch_file=$1
extra_commit_msg=$2
manual_commit=$3
if test -z "$manual_commit" -a "$extra_commit_msg" = --only-commit; then
    manual_commit=$extra_commit_msg
    extra_commit_msg=
fi
if test $# -gt 3 -o '!' -r "$patch_file" -o '!' '(' \
        -z "$manual_commit" -o "$manual_commit" = --only-commit ')'; then
    echo "Usage: $0 PATCH_FILE [EXTRA_MSG] [--only-commit]" >&2
    exit 1
fi

head=$(sed -e '1,/^\(diff\|---\)/!d' "$patch_file")

commit=$(echo "$head" | sed -ne 's/^commit[[:blank:]]\+\(.*\)/\1/p' | head -n1)
author=$(echo "$head" | sed -ne 's/^Author:[[:blank:]]\+\(.*\)/\1/p' | head -n1)
author_name=$(echo "$author" | sed -e 's/ <.*//')
author_email=$(echo "$author" | sed -ne 's/.*<\(.*\)>.*/\1/p')
date=$(echo "$head" | sed -ne 's/^Date:[[:blank:]]\+\(.*\)/\1/p' | head -n1)

commit_msg=$(echo "$head" | sed -e '/^    \|^$/!d;s/^    //')
commit_msg=$(
    printf '\n\n%s\n\n(git-reapply-patch cherry-pick %s)\n%s' \
      "$commit_msg" "$commit" "$extra_commit_msg" |
    sed -e '1,/^[^[:blank:]]/{/^[[:blank:]]*$/d}')

printf "author_name='%s'\n" "$author_name"
printf "author_email='%s'\n" "$author_email"
printf "date='%s'\n" "$date"
printf "commit_msg='%s'\n" "$(echo "$commit_msg" | sed -e "s/'/'\\''/g")"
echo

# exit 3  # <-- uncomment to test output

if test "$manual_commit" = --only-commit; then
    if test -z "$(git status --porcelain | grep -v '^??')"; then
        echo "Nothing to commit; did you do the manual staging?" 2>&1
        exit 1
    fi
elif test -n "$(git status --porcelain | grep -v '^??')"; then
    echo "Please clear the staging area first" >&2
    exit 1
elif ! git apply --index "$patch_file"; then
    exit 1
fi

# Optional
#GIT_COMMITTER_DATE=$date
#GIT_COMMITTER_NAME=$author_name
#GIT_COMMITTER_EMAIL=$author_email

# Using --no-gpg-sign by default, perhaps because signing takes extra
# manual confirmation. You may want to alter that.
GIT_AUTHOR_DATE=$date \
GIT_AUTHOR_NAME=$author_name \
GIT_AUTHOR_EMAIL=$author_email \
git commit --no-gpg-sign -m "$commit_msg" || exit $?