vimdiff

#!/bin/sh
help() {
  if [ "$full_help" = 1 ] || [ ! -t 1 ] || [ "$(tput lines)" -gt 99 ]; then
    # Run `vim --help`, update the name, print after line 2
    usage=$("$vim" --help 2>$dn |awk -vi=" $self " '{ sub(" vim ", i) } NR > 2')
    tall=1
  fi
  cat <</help
Drop-in replacement for [g]vimdiff.
Given one file, compares to git, SyncThing, snapshots, or else backup names.

${usage:-Usage: vimdiff [arguments] [file ...]}

Arguments recognized by vimdiff-auto wrapper (@adamhotep misc-scripts):
   --full-help          Include vim command-line help$([ -n "$tall" ] && echo "
   --help               Display this command-line help and exit
   --test, --noop       Report the vim command but do not run it
   --version            Display vim & vimdiff-auto version info and exit")
   --exec <path>        VIM executable, currently \`$vim\`
   --snapshot <path>    Snapshot directory (absolute or relative to the file).
                        ZFS snapshots are auto-detected UNLESS this path exists.
                        Non-ZFS snapshots (e.g. for NetApps) are experimental.
                        Currently \`$snapshot\`
   --syncthing <path>   SyncThing versions directory (relative or absolute).
                        Currently \`$syncthing\`

Install ahead of vimdiff in your \$PATH like /usr/local/bin/vimdiff and create a
symlink named gvimdiff that points to it (if you have gvim installed).

/help
  version
}

# Debug mode is supported by running as `sh -x /path/to/this/vimdiff`
# You can alternatively use bash or zsh for ~better xtrace information.

version() { cat <</version
Wraps $(vim_version "vim (version unknown, '$vim --help' failed)")
Part of misc-scripts: https://github/adamhotep/misc-scripts
vimdiff-auto 2.2.20240810.1 copyright 2009+ by Adam Katz, GPLv3
/version
  exit
}

# Usage: vim_version FALLBACK_TEXT
# Parse `vim --help` and get the version (line 1) or else show FALLBACK_TEXT
vim_version() {
  # GNU, BSD, and Busybox all support `grep -m NUMBER`
  "$vim" --help 2>$dn |grep -m1 . || echo "$*"
}

# Version 1.x (`vimdiff+cvs`) could also automatically traverse CVS & Subversion
# repositories, but that functionality has been removed in favor of git.
#
# While this script can properly invoke git itself, you can additionally put
# `vimdiff = difftool -y -t vimdiff` in the `[alias]` section of ~/.gitconfig
# (and the same for `gvimdiff`) to be able to run `git vimdiff bar.txt`

# Escape glob characters.
escape_glob() { echo "$*" |sed 's/[\]\[\\*?]/\\&/g'; }

# We need to do some crazy escaping for the nested call to git.
# Escape single-quotes; `I'm happy` -> `'I'\''m happy'`
# This could probably use some more security vetting.
escape_squot() { gitcmd="$gitcmd '$(echo "$*" |sed "s/'/'\\''/g")'"; }

# Usage: differ OLD FILE
# Prints OLD and returns true when OLD is a nonzero file NOT identical to FILE
differ() {
  if [ -f "$1" ] && [ -s "$1" ] && ! diff -q "$@" >$dn; then
    echo "$1"
    return 0
  fi
  return 1
}

# Usage: git_diff [DIR] FILE
# If git tracks FILE, vimdiff it vs git HEAD (even if there are no differences)
git_diff() {
  local owd="$PWD"
  if ! command -v git >$dn; then
    : "git is not installed, skipping git diff"
    return 1
  fi
  : "Seeking a git revision for <$1>"
  if [ "$PWD" != "${1%/*}" ]; then cd "${1%/*}"; fi
  #if git ls-files --error-unmatch "$1" 2>$dn; then	# git tracked?
  git diff --quiet "$last" 2>$dn
  case $? in
    ( 0 )  echo "$self: git repo found but <$1> is unchanged or untracked" ;;
    ( 1 )  : "Found a git revision of <$1> that differs"
           exec git difftool --no-prompt --extcmd="$gitcmd" -- "$1" ;;
    ( * )  : "Failed to find a git respository for <$1>" ;;
  esac
  if [ "$PWD" != "${1%/*}" ]; then cd "$owd"; fi
}

# Usage: syncthing_version FILE
# Find a potential SyncThing version of FILE
syncthing_version() {
  : "Seeking a SyncThing version for <$1>"
  local dir="$1" old fn fn_ver ext timestamp
  while dir="${dir%/*}" && [ -d "$dir" ]; do
    if [ -d "$dir/$syncthing" ]; then
      old="$dir/$syncthing/${last#$dir/}"	# trash can versioning
      differ "$old" "$1" && return 0
      fn="${last##*/}"
      fn_ver="$(escape_glob "$fn")"
      ext="${fn_ver##*.}"
      timestamp="~$ymd-$hms"
      if [ "$ext" != "$fn_ver" ]; then # we have an extension
        fn_ver="${fn_ver%.$ext}$timestamp.$ext"
      else
        fn_ver="$fn_ver$timestamp"
      fi
      find_eligible "$1" "$dir/$syncthing" -name "$fn_ver" && return 0
      break	# for speed & simplicity, assume there are no nested $syncthing
    fi
  done
  return 1
}

# Usage: find_eligible FILE PATH [PATH...] [FIND_OPTIONS]
# Report the most recent eligible file in the given PATHs. SUFFIX may be a glob.
find_eligible() {
  local file="$1" name or= old
  shift  # remove the FILE

  # GNU, BSD, and Busybox `find` all support -maxdepth, -mindepth, and -print0
  # even though they're not in the POSIX standard. Ditto for `xargs -0`.
  # The awk call makes the list unique without changing the order.
  # I believe it's `find` that is super slow on ZFS snapshots.
  find "$@" -type f -size +0 -print0 2>$dn |xargs -0 ls -td |awk '!seen[$0]++' \
    |while IFS= read -r old; do differ "$old" "$file" && return 0; done \
    |grep ^	# the `while` loop was in a subshell. this sets the return code.
}

# Usage: snapshot_version FILE [FIND_OPTIONS]
# Should support ZFS, NetApps, and more. Only ZFS is tested.
# Warning, ZFS is slow if there are lots of recent and identical snapshots.
# Expects a file of the same name as FILE 1-2 levels below the snapshot dir.
# Auto-senses the ZFS snapshot dir.
snapshot_version() {
  : "Seeking a snapshot for <$1>"
  local dir zfs= zfsdir= old= parent="${1%/*}/"
  case "$snapshot" in
    ( /* )	dir="$snapshot" ;;
    ( * )	dir="$parent$snapshot" ;;
  esac
  if [ ! -d "$dir" ]; then
    # *if* on a ZFS filesystem, set $zfs to the file's ZFS mount point
    # GNU, BSD, and Busybox all support `df -T`. Busybox lacks `df -t type`.
    zfs=$(df -T "$1" |awk '$2=="zfs" { gsub(/.*%[[:space:]]+\//, "/"); print }')
    dir="$zfs/.zfs/snapshot"
    zfsdir="$dir/${parent#$zfs/}"
    zfsdir="${zfsdir%/}"
    if [ "$zfsdir" = "$dir" ]; then zfsdir=""; fi
  fi
  if [ -d "$dir" ]; then
    : "Seeking newest different snapshot of <${1#$zfs/}> in <$dir>"
    find_eligible "$@" "$dir" ${zfs:+"$zfsdir"} \
      -name "$(escape_glob "${1##*/}")" -mindepth 1 -maxdepth 2
    return $?
  fi
  return 1
}

# Usage: backup_copy FILE [FIND_OPTIONS]
# Support common backup file names
backup_copy() {
  : "Seeking a backup filename for <$1>"
  local file="$1" base="$(escape_glob "${1##*/}")" ext or=
  shift
  set -- "$file" "${file%/*}" -maxdepth 1 "$@" '('

  # Here is the list of suffix patterns we accept. Note the non-suffix later.
  for ext in '~' .backup .bak .new .old .orig .rej .tmp \
    ".$ymd" ".$ymd$hms" ".$ymd[-_.]$hms" \
    '.*[-.]dist' '.*[-.]new' '.*[-.]old' '.*[-.]tmp' '.rpm[nos][era][wgv]*'
  do
    set -- "$@" $or -name "$base$ext"
    or='-o'
  done
  # add `#file#` (not just a suffix) and the end-parenthesis
  set -- "$@" $or -name "#$base#" ')'

  find_eligible "$@"
}

# Defaults
self="${0##*/}"
snapshot="${SNAPSHOT_DIR:-.snapshot}"
syncthing=".stversions"
default_vim="vim"
vim="$default_vim"

# Constants and initializations
dn='/dev/null'
d='[0-9]'
ymd="20$d$d[01]$d[0-3]$d"
hms="[012]$d[0-5]$d[0-6]$d"
last=""
penultimate=""
reset=0
opt=1
skip=0
full_help=0
tall=""
gitcmd="$0 --nofork"
noop=""

# special case for just -V (if you actually want that, use `-V10`)
if [ "$*" = -V ]; then version; fi

# Loop through the arguments, find -h/--help, note the last two files (if any).
# This is a little messy because vim accepts options EVERYWHERE except after --
for arg in "$@"; do
  : "Parsing arg <$arg>"
  if [ "$reset" = 0 ]; then reset=1; set --; fi	# reset the $@ array
  if [ "$opt" = 1 ]; then
    if [ "$skip" != 0 ]; then
      case "$skip" in
        ( exec )	vim="$arg" ;;		# alternate vim executable
        ( snapshot )	snapshot="$arg" ;;	# Snapshot directory
        ( syncthing )	syncthing="$arg" ;;	# SyncThing versions directory
        ( 1 )	escape_squot "$arg"; set -- "$@" "$arg" ;;	# vim option arg
      esac
      skip=0
      continue
    elif [ "$arg" != "${arg#[-+]?}" ]; then
      push=
      case "$arg" in
        # options with required arguments: cue skipping
        ( --cmd | -[!-]*[tqcSiPrsTuUwW] | -[tqcSiPrsTuUwW] \
        | --gui-dialog-file | --log | --remote-expr | --remote-send \
        | --servername | --socketid | --startuptime | --windowid ) skip=1 ;;
        # options that we intercept and use locally
        ( -- )			opt=0 ;;
        ( --exec*=* )		vim="${arg#*=}" ;;
        ( --exec )		skip=exec ;;
        ( --full-help ) 	full_help=1; help ;;
        ( --help | -[h?]* | -[!-]*[h?]* )	help ;;
        ( --noop | --test )	noop="echo" gitcmd="echo ${gitcmd#echo }" ;;
        ( --snap*=* )		snapshot="${arg#*=}" ;;
        ( --snap* ) 		skip=snapshot ;;
        ( --syncthing*=* )	syncthing="${arg#*=}" ;;
        ( --syncthing* )	skip=syncthing ;;
        ( --version )		version ;;
        # other vim options
        ( * )			push=1 ;;
      esac
      if [ "$skip" = 1 ] || [ "$push" = 1 ]; then
        escape_squot "$arg"
        set -- "$@" "$arg"
      fi
      continue
    fi
  fi
  if [ -e "$last" ]; then penultimate="$last"; fi
  if [ -e "$arg" ]; then last="$arg"; fi
  set -- "$@" "$arg"
done

# no file arguments: open a diff between two new files
if [ ! -e "$last" ]; then
  set -- "$@" +'vsp|enew|diffthis'

# Just one file
elif [ -z "$penultimate" ]; then
  last=$(readlink -f "$last")	# we want the true path, not a symlink ...right?

  git_diff "$last"	# If there's a git revision to diff, do that and exit

  # we're taking full advantage of vim's ability to take options anywhere
  # and avoiding the need to inject $penultimate immediately before $last
  if penultimate="$(syncthing_version "$last")"; then
    : "Found a syncthing version of <$last>"
    set -- "$penultimate" "$@"
  elif penultimate="$(snapshot_version "$last")"; then
    : "Found a snapshot copy of <$last>"
    set -- "$penultimate" "$@"
  elif penultimate="$(backup_copy "$last")"; then
    : "Found a backup copy of <$last>"
    set -- "$penultimate" "$@"
  else
    apology='echo "(Could not find a git, snapshot, or backup copy to diff)"'
    set -- "$@" +"vsp|enew|diffthis|$apology"
  fi
fi

if [ "$vim" != "$default_vim" ]; then
  : "Running nondefault vim <$vim> rather than guessing GUI"
  : "Consider using \`-g\` force vim to run the GUI"
  exec $noop "$vim" -d "$@"
fi

undef() { echo "Undefined script name '$self', guessing $* vim" >&2; }

case "$self" in
  ( vimdiff* )	exec $noop "$vim" -d "$@" ;;
  ( *vimdiff* )	exec $noop "$vim" -gd "$@" ;;
  ( [gkwx]* ) 	undef graphical; exec $noop "$vim" -gd "$@" ;;
  ( * ) 	undef console; exec $noop "$vim" -d "$@" ;;
esac