How do I save changed files?

I have two folders:

ORIGINAL/
ORIGINAL_AND_MY_CHANGES/

My friend has a copy of ORIGINAL/. I would like to generate MY_CHANGES.tgz — it should contain only new/changed files from ORIGINAL_AND_MY_CHANGES/ comparing to ORIGINAL/. So my friend can unpack it into his copy of ORIGINAL/ and get ORIGINAL_AND_MY_CHANGES/.

How can I do this?

P.S. I tried diff but it can’t save binary data and rsync --link-dest — it generates hard links which are useless in the archive.

P.P.S. In my case modification time can’t be used to decide which file was changed.

Answers:

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Method 1

With rsync

What you’re doing is essentially an incremental backup: your friend (your backup) already has the original files, and you want to make an archive containing the files you’ve changed from that original.

Rsync has features for incremental backups.

cd ORIGINAL_AND_MY_CHANGED
rsync -a -c --compare-dest=../ORIGINAL . ../CHANGES_ONLY

• -a means to preserve all attributes (times, ownership, etc.).
• -c means to compare file contents and not rely on date and size.
• --compare-dest=/some/directory means that files which are identical under that directory and the source tree are not copied. Note that the path is relative to the destination directory.

Rsync copies all directories, even if no files end up there. To get rid of these empty directories, run find -depth CHANGES_ONLY -type d -empty -delete (or if your find doesn’t have -delete and -empty, run find -depth CHANGES_ONLY -exec rmdir {} + 2>/dev/null).

Then make the archive from the CHANGES_ONLY directory.

The pedestrian way

Traverse the directory with your file. Skip files that are identical with the original. Create directories in the target as necessary. Copy changed files.

cd ORIGINAL_AND_MY_CHANGES
find . ! -type d -exec sh -c '
  for x; do
    if cmp -s "$x" "../ORIGINAL/$x"; then continue; fi
    [ -d "../CHANGES_ONLY/$x" ] || mkdir -p "../CHANGES_ONLY/${%/*}"
    cp -p "$x" "../CHANGES_ONLY/$x"
  done
' {} +

Method 2

The command

rsync --only-write-batch=FILE $other_options ORIGINAL_AND_MY_CHANGES/ ORIGINAL/

would produce a batch FILE containing the changes required (without modifying anything).

The patch could be applied on another site, where you take the batch FILE, with

rsync --read-batch=FILE ORIGINAL/

All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0