tsibley · August 1, 2024 17:10
diff --git a/git-diff-rebase b/git-diff-rebase
 #!/bin/bash
 # usage: git diff-rebase
 #        git diff-rebase u[pstream]
 #        git diff-rebase <a> [<b>] [<branch>]
 #        git diff-rebase -h
 #
 # Display the differences in a branch after rebasing it.
 #
 # Immediately after a rebase, running this command with no arguments displays
 # differences between the pre- and post-rebase versions of the current branch
 # using "git range-diff".  This is very handy to check that the result of the
 # rebase you just performed matches your expectations.
 #
 # If the sole argument "u" or "upstream" is provided, the differences between
 # the remote tracking branch and your local branch are displayed.  This is
 # handy when you've done several rebases in a row and want to compare your
 # expectations to what you pushed previously.
 #
 # For advanced and uncommon use cases, up to three arguments may be provided to
 # partially or fully specify the reflog entries to compare.  The first two
 # arguments, <a> and <b>, specify the branch reflog entries to compare and
 # default to 1 and 0.  The third argument, <branch>, specifies the branch name
 # whose reflog to use, with HEAD allowed as an alias for the current branch.
 # (Note that the current branch's reflog is distinct from HEAD's reflog
 # normally.)  All together, these three values identify the two reflog entries
 # to compare in the form of <branch>@{<a>} and <branch>@{<b>}.  Refer to the
 # documentation of "git rev-parse", § "Specifying revisions" for an explanation
 # of what these mean.  The merge base is always assumed to be relative to
 # master.  Set diff-rebase.base-branch to use a different branch.
 #
 # For an explanation of the diff format that's output, refer to the
 # documentation of "git range-diff".
 #
 # The DIFFOPTS environment variable may be set to pass extra options to "git
 # range-diff".
 #
 set -euo pipefail

 main() {
    for arg; do
        case "$arg" in
            --help|-h)
                usage
                exit 0;;
        esac
    done

    local branch="$(branch-name "${3:-HEAD}")"
    local a="$branch@{${1:-1}}"
    local b="$branch@{${2:-0}}"

    exec git range-diff ${DIFFOPTS:-} \
        "$(branch-merge-base $a)..$a" \
        "$(branch-merge-base $b)..$b"
 }

 branch-name() {
    case "$1" in
        HEAD)
            # Resolve HEAD to a branch name name to access its reflog.  This is
            # necessary because we don't want HEAD's reflog, which changes on
            # each checkout.
            git symbolic-ref --short HEAD;;
        *)
            # Ensure the passed ref is a parseable branch name
            git rev-parse --revs-only --symbolic "$1" --;;
    esac
 }

 branch-merge-base() {
    git merge-base "$(git config --default master --get trs.diff.base)" "$1"
 }

 usage() {
    local line
    while read -r line; do
        if [[ $line =~ ^#! ]]; then
            continue
        elif [[ $line =~ ^# ]]; then
            line="${line/##/}"
            line="${line/# /}"
            echo "$line"
        else
            break
        fi
    done < "$0"
 }

 main "$@"
	#!/bin/bash
	# usage: git diff-rebase
	# git diff-rebase u[pstream]
	# git diff-rebase <a> [<b>] [<branch>]
	# git diff-rebase -h
	#
	# Display the differences in a branch after rebasing it.
	#
	# Immediately after a rebase, running this command with no arguments displays
	# differences between the pre- and post-rebase versions of the current branch
	# using "git range-diff". This is very handy to check that the result of the
	# rebase you just performed matches your expectations.
	#
	# If the sole argument "u" or "upstream" is provided, the differences between
	# the remote tracking branch and your local branch are displayed. This is
	# handy when you've done several rebases in a row and want to compare your
	# expectations to what you pushed previously.
	#
	# For advanced and uncommon use cases, up to three arguments may be provided to
	# partially or fully specify the reflog entries to compare. The first two
	# arguments, <a> and <b>, specify the branch reflog entries to compare and
	# default to 1 and 0. The third argument, <branch>, specifies the branch name
	# whose reflog to use, with HEAD allowed as an alias for the current branch.
	# (Note that the current branch's reflog is distinct from HEAD's reflog
	# normally.) All together, these three values identify the two reflog entries
	# to compare in the form of <branch>@{<a>} and <branch>@{<b>}. Refer to the
	# documentation of "git rev-parse", § "Specifying revisions" for an explanation
	# of what these mean. The merge base is always assumed to be relative to
	# master. Set diff-rebase.base-branch to use a different branch.
	#
	# For an explanation of the diff format that's output, refer to the
	# documentation of "git range-diff".
	#
	# The DIFFOPTS environment variable may be set to pass extra options to "git
	# range-diff".
	#
	set -euo pipefail

	main() {
	for arg; do
	case "$arg" in
	--help\|-h)
	usage
	exit 0;;
	esac
	done

	local branch="$(branch-name "${3:-HEAD}")"
	local a="$branch@{${1:-1}}"
	local b="$branch@{${2:-0}}"

	exec git range-diff ${DIFFOPTS:-} \
	"$(branch-merge-base $a)..$a" \
	"$(branch-merge-base $b)..$b"
	}

	branch-name() {
	case "$1" in
	HEAD)
	# Resolve HEAD to a branch name name to access its reflog. This is
	# necessary because we don't want HEAD's reflog, which changes on
	# each checkout.
	git symbolic-ref --short HEAD;;
	*)
	# Ensure the passed ref is a parseable branch name
	git rev-parse --revs-only --symbolic "$1" --;;
	esac
	}

	branch-merge-base() {
	git merge-base "$(git config --default master --get trs.diff.base)" "$1"
	}

	usage() {
	local line
	while read -r line; do
	if [[ $line =~ ^#! ]]; then
	continue
	elif [[ $line =~ ^# ]]; then
	line="${line/##/}"
	line="${line/# /}"
	echo "$line"
	else
	break
	fi
	done < "$0"
	}

	main "$@"