7.8 Patch and Diff Programs

This section describes variables that specify the programs to be used for applying patches and for computing the main difference regions (not the fine difference regions):

ediff-patch-program

ediff-diff-program

ediff-diff3-program

These variables specify the programs to use to produce differences and do patching.

ediff-patch-options

ediff-diff-options

ediff-diff3-options

These variables specify the options to pass to the above utilities.

In ediff-diff-options, it may be useful to specify options such as `-w' that ignore certain kinds of changes. However, Ediff does not let you use the option `-c', as it doesn't recognize this format yet.

ediff-custom-diff-program

ediff-custom-diff-options

Because Ediff limits the options you may want to pass to the diff program, it partially makes up for this drawback by letting you save the output from diff in your preferred format, which is specified via the above two variables.

The output generated by ediff-custom-diff-program (which doesn't even have to be a standard-style `diff'!) is not used by Ediff. It is provided exclusively so that you can refer to it later, send it over email, etc. For instance, after reviewing the differences, you may want to send context differences to a colleague. Since Ediff ignores the `-c' option in ediff-diff-program, you would have to run diff -c separately just to produce the list of differences. Fortunately, ediff-custom-diff-program and ediff-custom-diff-options eliminate this nuisance by keeping a copy of a difference list in the desired format in a buffer that can be displayed via the command D.

ediff-patch-default-directory

Specifies the default directory to look for patches.

Warning: Ediff does not support the output format of VMS diff. Instead, make sure to use some implementation of POSIX diff, such as gnudiff.