GIT: Creates a cumulative patch from the specified commit to the current HEAD.

squash-patch.sh

#!/bin/sh

# Won’t work if a branch called _squash_patch_tmp already exists.
# And probably many other caveats?

REFS_NAMED_HEAD=`git show-ref --heads --tags | grep "^[0-9a-f]\{40\} refs/\(heads\|tags\)/HEAD$"`;
if [ "$REFS_NAMED_HEAD" ]; then
  echo "HEAD is ambiguous.";
  exit 2
fi

if [ -z "$1" ]; then
  echo "Syntax: squash-patch.sh FROM"
  exit 1
fi

FROM_COMMIT=$1
git merge-base --is-ancestor "$FROM_COMMIT" HEAD
if [ $? -ne 0 ]; then
  echo "$FROM_COMMIT is not an ancestor of the current HEAD."
  exit 1
fi

# We want to return to the commit we were originally on. If we were on branch,
# return to that by name, not just to the commit hash.
BASE=`git rev-parse --abbrev-ref HEAD`
if [ "$BASE" = "HEAD" ]; then
  BASE=`git rev-parse HEAD`
fi

TMP_BRANCH=_squash_patch_tmp
set -x

git checkout "$FROM_COMMIT"
git checkout -b "$TMP_BRANCH"
git merge --squash "$BASE"
GIT_EDITOR=true git commit
git format-patch HEAD^
git checkout "$BASE"
git branch -D "$TMP_BRANCH"

set +x

ls *.patch