git-safemerge performs a "safer" merge, confirming the commits to be merged and the changes to be made before starting the commit process.

git-safemerge

#!/bin/bash
# Performs a "safe" merge, confirming the commits to be merged, the merge
# strategy, any conflicts, etc.
# Useage:
#     $ git safemerge master
#     Commits:
#      * bc911ef Fix bug in widget
#      * e80f8d1 Clean things up
#
#     Changes:
#      foo.py   |  12 ++--
#      bar.py   |  35 +++++-----
#      2 files changed, 47 insertions(+), 47 deletions(-)
#
#     Fast-forward: not possible
#
#     Continue merging master into prod? (y/n)
#
# Installation:
#     Copy git-safemerge to ~/bin/ or /usr/local/bin/, or wherever you prefer to
#     keep such things.

version="0.1.1"

C_RED='\033[0;31m'
C_GREEN='\033[0;32m'
C_YELLOW='\033[0;33m'
C_RESET='\033[0m'


IFS="`printf "\n\t"`"
set -eu

if [[ "$#" != "1" || "$1" == "-h" ]]; then
    echo "usage: git safemerge [--version] <commit>"
    echo
    echo "Performs a \"safe\" merge, confirming the commits to be merged,"
    echo "the merge strategy, any conflicts, etc."
    exit 1
fi

if [[ "$1" == "--version" ]]; then
    echo "git-safemerge version $version"
    exit 0
fi

merge_target="$1"
cur_branch="$(git rev-parse --abbrev-ref HEAD)"

target_hash="$(git rev-parse --verify --quiet "$merge_target")" || res=$?
if [[ "${res-}" -gt 0 ]]; then
    if [[ "$res" -lt 128 ]]; then
        echo "fatal: $merge_target - not something we can merge" >&2
    fi
    exit $res
fi

merge_base="$(git merge-base HEAD "$merge_target")"
if [[ "$target_hash" == "$merge_base" ]]; then
    echo -e "${C_YELLOW}$cur_branch${C_RESET} already up-to-date with ${C_YELLOW}$merge_target${C_RESET}."
    exit 0
fi

echo "Commits:"
git log --color --oneline --graph HEAD.."$merge_target" | sed -e 's/^/ /g'

echo
echo "Changes:"
git diff --stat HEAD..."$merge_target"

echo
if git merge-base --is-ancestor HEAD "$merge_target"; then
    echo -e "Fast-forward: ${C_GREEN}possible${C_RESET}"
else
    echo -e "Fast-forward: ${C_RED}not possible${C_RESET}"
fi

echo
echo -ne "Continue merging ${C_YELLOW}$merge_target${C_RESET} into ${C_YELLOW}$cur_branch${C_RESET}? (y/n) "
read do_merge
do_merge="$(tr [A-Z] [a-z] <<< "$do_merge")"
if [[ ! ( "$do_merge" == "y" || "$do_merge" == "yes" ) ]]; then
    exit 1
fi

git merge --verbose --edit  "$merge_target"