(diff.info.gz) Avoiding Common Mistakes

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 Avoiding Common Mistakes
 ========================
 
    When producing a patch for multiple files, apply `diff' to
 directories whose names do not have slashes.  This reduces confusion
 when the patch consumer specifies the `-pNUMBER' option, since this
 option can have surprising results when the old and new file names have
 different numbers of slashes.  For example, do not send a patch with a
 header that looks like this:
 
      diff -Naur v2.0.29/prog/README prog/README
      --- v2.0.29/prog/README	2002-03-10 23:30:39.942229878 -0800
      +++ prog/README	2002-03-17 20:49:32.442260588 -0800
 
 because the two file names have different numbers of slashes, and
 different versions of `patch' interpret the file names differently.  To
 avoid confusion, send output that looks like this instead:
 
      diff -Naur v2.0.29/prog/README v2.0.30/prog/README
      --- v2.0.29/prog/README	2002-03-10 23:30:39.942229878 -0800
      +++ v2.0.30/prog/README	2002-03-17 20:49:32.442260588 -0800
 
    Make sure you have specified the file names correctly, either in a
 context diff header or with an `Index:' line.  Take care to not send out
 reversed patches, since these make people wonder whether they have
 already applied the patch.
 
    Avoid sending patches that compare backup file names like
 `README.orig' or `README~', since this might confuse `patch' into
 patching a backup file instead of the real file.  Instead, send patches
 that compare the same base file names in different directories, e.g.
 `old/README' and `new/README'.
 
    To save people from partially applying a patch before other patches
 that should have gone before it, you can make the first patch in the
 patch file update a file with a name like `patchlevel.h' or
 `version.c', which contains a patch level or version number.  If the
 input file contains the wrong version number, `patch' will complain
 immediately.
 
    An even clearer way to prevent this problem is to put a `Prereq:'
 line before the patch.  If the leading text in the patch file contains a
 line that starts with `Prereq:', `patch' takes the next word from that
 line (normally a version number) and checks whether the next input file
 contains that word, preceded and followed by either white space or a
 newline.  If not, `patch' prompts you for confirmation before
 proceeding.  This makes it difficult to accidentally apply patches in
 the wrong order.
 

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(diff.info.gz) Tips for Patch Consumers

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(diff.info.gz) Generating Smaller Patches