git-sed

#!/bin/bash
# Copyright 2015 Mark Lodato <lodato@google.com>
# Released under the MIT license; see LICENSE for details.

SUBDIRECTORY_OK=Yes
OPTIONS_SPEC="\
git sed <sed-args> <script-if-no-other-script> [--] [<file>...]

Similar to git-grep, git-sed uses git to generate the candidate list of
files to pass to sed.  Advantages over regular sed include:
* An empty list of files means all git-tracked files within the current
  directory, recursively.
* Listing a directory includes all (git-tracked) files in it.
* Output is sent to the git pager (use 'git --no-pager' to disable).

Note that this filters out anything that is not a regular file or a symlink to
a regular file.
--
dry-run         print the sed command that would have been run
error-unmatch   (default) return error if any <file> does not match

 GNU sed options
n,quiet         suppress automatic printing of pattern space
silent*         same as --quiet
e,expression=   add script to the commands to be executed
f,file=         add contents of file to the commands to be executed
follow-symlinks follow symlinks when processing in place
i,in-place?     edit files in place (makes backup if SUFFIX supplied)
l,line-length   desired line-wrap length for the \`l' command
posix           disable all GNU extensions
r,regexp-extended use extended regular expressions in the script
s,separate      consider files as separate rather than as a single continuous long stream
u,unbuffered    load minimal amounts of data from the input files and flush the output buffers more often
z,null-data     separate lines by NUL characters
version         output version information and exit
"

# We need to pass --stuck-long to git-rev-parse in order to uniqely identify
# whether or not -i/--in-place took an argument.  Unfortunately git-sh-setup
# does not have an option to pass --stuck-long to git-rev-parse, so we have to
# fool it into letting us handle $@.  We cannot just unset OPTIONS_SPEC since
# that causes it to interpret the -h option.  Instead, we do two passes of
# git-rev-parse, the first time passing in all the arguments as positionals.
set -- -- "$@"
. "$(git --exec-path)/git-sh-setup"
require_work_tree
shift  # leading -- that was added above

set -o pipefail

# Normalize the options, exiting on invalid args or -h.
eval "$(
    echo "$OPTIONS_SPEC" |
        git rev-parse --parseopt --stuck-long -- "$@" ||
        echo exit $?
)"

# Parse the options.
declare -i has_script=0
declare dry_run=""
declare error_unmatch="--error-unmatch"
while (( $# > 0 )); do
    case "$1" in
        --)
            shift
            break
            ;;
        --error-unmatch|--no-error-unmatch)
            error_unmatch="$1"
            ;;
        --dry-run)
            dry_run="echo"
            ;;
        --expression=*|--file=*)
            has_script=1
            sed_args=( "${sed_args[@]}" "$1" )
            ;;
        *)
            sed_args=( "${sed_args[@]}" "$1" )
            ;;
    esac
    shift
done

# If there was no -e or -f flag, then the first positional argument is the
# script, not a filename.
if (( !has_script )); then
    if (( $# == 0 )); then
        die "ERROR: missing script"
    fi
    sed_args=( "${sed_args[@]}" --expression="$1" )
    shift
fi

# Filters out anything that is not a regular file.  Input and output are both
# NUL-terminated.
filter_regular_files() {
    while IFS= read -d $'\0' -r file; do
        [[ -f "$file" ]] && printf '%s\0' "$file"
    done
}

git ls-files $error_unmatch -z -- "$@" \
    | filter_regular_files \
    | xargs --null --no-run-if-empty $dry_run sed "${sed_args[@]}" -- \
    | git_pager