====== Diff and patch Usage ==
===== Genral diff usage ==

Compare differences between 2 text files

| -y | side by side compare; "%%|%%" indicates differences |
| -s | Report when two files are the same |
| -r | Recursively compare any subdirectories found |
| -w | Ignore changes in white space |
| -N | treat absent files as empty |
| -a | treat all files as text |
| -u | output NUM (default 3) lines of unified context |

Use ''cmp'' for binary files.

===== Create a patch file ==

Initital situation: You have the source tree of the original project and your improved version of the project:

  .
  |-- project.org/
  `-- project.new/

Create the patch file with:

  diff -Naur project.org project.new > improvement.patch

If your editor is set to change the amount of whitespace (which may be useful, eg. when it automatically deletes trailing spaces) in ''project.new/'' than you shold ignore this in the diff command in order not to confuse the receiver of the patch:

  diff -Naurw project.org project.new > improvement.patch

===== Apply the patch file ==

Initital situation: You have the source tree of the project to be patched and the patch file:

  .
  |-- project.toBePatched/
  `-- improvement.patch

Patch the project with:

<code bash>
  cd project.toBePatched
  patch -p1 < ../improvement.patch
</code>

You can test also try out first what the patch actually would do withou changing anything:

  patch -p1 --dry-run < ../improvement.patch

More info at http://www.kegel.com/academy/opensource.html#patches