git-find-match

#!/bin/bash

usage() {
  local p=$(basename $0)
  cat <<EOF >&2
$p - List changed file that may be in other version tree
Usage: $p <tag>
Example:
  // current state is based on v2.6.32
  $ git log -1 --oneline
  22763c5cf369 (HEAD -> dsm232-port, tag: v2.6.32) Linux 2.6.32

  // list changed files that seems to be in v2.6.32.45
  $ $p v2.6.32.45 | head -3
  Documentation/Changes
  Documentation/DocBook/Makefile
  Documentation/filesystems/ext4.txt

  // revert matching files to state as of v2.6.32
  $ $p v2.6.32.45 | xargs -n1 git checkout -f v2.6.32 --
  // remove those failed to revert back (= nonexistent as of v2.6.32)
  $ $p v2.6.32.45 | xargs rm
  // same as above, but more efficient
  $ $p v2.6.32.45 | \\
  xargs -n1 -I{} sh -c "git checkout -f v2.6.32 -- '{}' || rm '{}'"
EOF
  exit 1
}

run() {
  local tag=$1

  # on Linux, bash allocates fd#63, 62, ... for in-place pipes created
  textql -sql "SELECT * FROM '63' EXCEPT SELECT * FROM '62'" \
  <(git ls-files -om) \
  <(git diff --name-only $tag) \
  | xargs git ls-files --with-tree=$tag --
}

test $# -gt 0 || usage
run "$@"