diff-project

# Copyright 2024 Google LLC

# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at

#     https://www.apache.org/licenses/LICENSE-2.0

# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

#!/bin/sh -e
set -eu

FILETYPES_DIR="$(dirname "$0")/filetypes"
SUPPORTED_EXTS='string containing extensions'

# Prints usage and quits
usage() {
    if [ -n "${2-}" ]; then
        echo "$2" >&2
    fi
    cat >&2 <<USAGE
USAGE: $0 [FROM_REV [FROM_DIR] [TO_REV [TO_DIR]]]
Compares all files matching the following:$SUPPORTED_EXTS
  FROM_REV - The revision to compare from.
             If unspecified, assumes origin/HEAD (the latest pushed commit).
  FROM_DIR - The directory to compare from.
             If unspecified, assumes the current directory.
  TO_REV   - The revision to compare to.
             Can only be specified if FROM_REV is specified.
             If unspecified, assumes the current working tree (your checkout).
  TO_DIR   - The directory to compare to.
             Can only be specified if TO_DIR is specified.
             If unspecified, assumes the same proj as FROM_DIR.
USAGE
    exit "${1-0}"
}

# Grabs the specified revision (or working tree) and generates a PDF
# $1: the from revision, or the empty string to use the working tree
# $2: the path to compare in the from revision
# $3: the to revision, or the empty string to use the working tree
# $4: the path to compare in the to revision
difffile() {
    ext="$(echo "$2" | sed -n "$SUPPORTED_EXTS")"
    test -n "$ext" || return 0
    if [ -z "$1" ]; then
        from="$2"
        test -f "$from" || from=''
    else
        from="$TEMP_DIR/from.${2##*/}"
        git show "$1:$2" > "$from" 2>/dev/null || from=''
    fi
    if [ -z "$from" ]; then
        echo "$2 does not exist in ${1:-the working tree}"
        return 1
    fi
    if [ -z "$3" ]; then
        to="$4"
        test -f "$to" || to=''
    else
        to="$TEMP_DIR/to.${4##*/}"
        git show "$3:$4" > "$to" 2>/dev/null || to=''
    fi
    if [ -z "$to" ]; then
        echo "$4 does not exist in ${3:-the working tree}"
        return 1
    fi
    "$FILETYPES_DIR/$ext.py" "$from" "$to" || return
}

# Lists all files from the chosen revision, stripping out $2
# You can add $2 to each line to reproduce the original path
# $1: the revision, or the empty string to use the working tree
# $2: the directory to compare
listfiles() {
    if [ -z "$1" ]; then
        git ls-files --cached --exclude-standard -- "$2"
    else
        git ls-tree --name-only -r "$1" "$2"
    fi | {
        str="$2"
        while read -r file; do
            # FIXME: This prefix handling is totally broken.
            file="./$file"
            printf '%s\n' "${file#$str}"
        done
    }
}


# Get parameters
FROM_REV=''
FROM_DIR=''
TO_REV=''
TO_DIR=''
while [ "$#" != 0 ]; do
    if [ "$1" = -h ]; then
        usage 0
    elif [ -e "$1" ]; then
        if [ -z "$FROM_DIR" ]; then
            FROM_DIR="$1"
        elif [ -z "$TO_DIR" ]; then
            TO_DIR="$1"
        else
            usage 2
        fi
    elif [ -z "$FROM_REV" ]; then
        FROM_REV="$1"
    elif [ -z "$TO_REV" ]; then
        TO_REV="$1"
    else
        usage 2
    fi
    shift
done
: "${FROM_REV:=origin/HEAD}"
: "${FROM_DIR:=.}"
: "${TO_DIR:="$FROM_DIR"}"
# FIXME: this prefix handling is totally broken
if [ "$FROM_DIR" != '.' ]; then
    FROM_DIR="./${FROM_DIR#./}"
fi
if [ "$TO_DIR" != '.' ]; then
    TO_DIR="./${TO_DIR#./}"
fi
FROM_DIR="${FROM_DIR%/}"
TO_DIR="${TO_DIR%/}"

TEMP_DIR="$(mktemp -d)"
trap 'rm -rf "$TEMP_DIR"' INT HUP 0

# Get a list of all files in both revisions
{
    listfiles "$FROM_REV" "$FROM_DIR"
    listfiles "$TO_REV" "$TO_DIR"
} | sort -u | {
    ret=0
    while read -r file; do
        difffile "$FROM_REV" "$FROM_DIR$file" "$TO_REV" "$TO_DIR$file" || ret=$?
    done
    exit "$ret"
} || exit "$?"