11.4 Generating Smaller Patches

The simplest way to generate a patch is to use ‘diff -Naur’ (see section Tips for Patch Producers), but you might be able to reduce the size of the patch by renaming or removing some files before making the patch. If the older version of the package contains any files that the newer version does not, or if any files have been renamed between the two versions, make a list of rm and mv commands for the user to execute in the old version directory before applying the patch. Then run those commands yourself in the scratch directory.

If there are any files that you don't need to include in the patch because they can easily be rebuilt from other files (for example, ‘TAGS’ and output from yacc and makeinfo), exclude them from the patch by giving diff the ‘-x pattern’ option (see section Comparing Directories). If you want your patch to modify a derived file because your recipients lack tools to build it, make sure that the patch for the derived file follows any patches for files that it depends on, so that the recipients' time stamps will not confuse make.

Now you can create the patch using ‘diff -Naur’. Make sure to specify the scratch directory first and the newer directory second.

Add to the top of the patch a note telling the user any rm and mv commands to run before applying the patch. Then you can remove the scratch directory.

You can also shrink the patch size by using fewer lines of context, but bear in mind that patch typically needs at least two lines for proper operation when patches do not exactly match the input files.