Generate Old Diff

Save the changes between two git commits into a pair of folders, one contains modified files and the other contains their original copy, and archive the folders to a compressed file. The file structure in the output would be like:

diff/
|-- old/
|   |-- fileA.c
|   |-- fileB.c
|   |-- dir1/
|       |-- fileC.c
|-- new/
    |-- fileA.c
    |-- fileB.c
    |-- dir1/
        |-- fileC.c

Usage

$ gen-old-diff.sh OUTPUT COMMIT_NEW [COMMIT_OLD]

• OUTPUT could be a folder or a compressed file, depends on the specified file extension. If the file extension does not match any valid compression method, the results would be a folder.
• COMMIT_NEW and COMMIT_OLD could be commit IDs or tags. If COMMIT_OLD is omitted, then difference between COMMIT_NEW and COMMIT_NEW~1 are generated.

Supported Compression Format

Currently, the script supports following compression formats and file extension:

Compression Format	File Extension
gzip	.tar.gz, .tgz
xz	.tar.xz, .txz
bzip2	.tar.bz2, .tbz2
compress	.tar.Z
Zip	.zip
7-Zip	.7z
RAR	.rar

Name of Result Folders

By default, the script saves the original files to old/ folder and the modified files to new/ folder. The folder name can be configured by OLD_DIR and NEW_DIR environment variables.

For example, saving diff results to original/ and modified/ folders

$ OLD_DIR=original NEW_DIR=modified gen-old-diff.sh /home/user/diff_results.zip c3fb102 103756c

Diff Results Double Checking

To double check diff results, specifing diff tools in DIRDIFFTOOL environment variable.

Example1: Using vimdiff with dirdiff plugin by adding the following to ~/.bashrc

function dirdiff() {
  vim -c "set diffopt+=iwhite" -c "DirDiff ${1} ${2}"
}
export -f dirdiff
export DIRDIFFTOOL=dirdiff

-- This also supports aborting diff generation by typing ":cq" on exit.

Example2: Use Meld for double checking

$ DIRDIFFTOLL=meld gen-old-diff.sh /home/user/diff_results.zip c3fb102 103756c