Known problems:

* The diffutils 2.7 documentation for `patch' is obsolete; this should be
  fixed in diffutils 2.8.  Until then, see `patch --help' or `man patch'.

Changes in version 2.3:

* Unless the POSIXLY_CORRECT environment variable is set:

  - `patch' now distinguishes more accurately between empty and
    nonexistent files if the input is a context diff.
    A file is assumed to not exist if its context diff header
    suggests that it is empty, and if the header timestamp
    is within 24 hours of 1970-01-01 00:00:00 UTC.
  - Files that ``become nonexistent'' after patching are now removed.
    When a file is removed, any empty ancestor directories are also removed.

* Files are now automatically gotten from RCS and SCCS
  if the -g or --get option is specified,
  or if the PATCH_GET environment variable is set
  and the -G or --no-get option is not specified.

* If the PATCH_VERSION_CONTROL environment variable is set,
  it overrides the VERSION_CONTROL environment variable.

* The method used to intuit names of files to be patched is now as follows:

  - Take the old and new names from the context header if present,
    and take the index name from the `Index:' line if present.
    Consider the file names to be in the order (old, new, index).
  - If some named files exist, use the first one if POSIXLY_CORRECT is set,
    the best one otherwise.
  - If no named files exist, some names are given, POSIXLY_CORRECT is not set,
    and the patch appears to create a file, then use the best name
    requiring the creation of the fewest directories.
  - Otherwise, ask the user for a file name.

  The ``best'' of a nonempty list of file names is defined as follows:
    - Take the names with the fewest path name components;
      of those, take the names with the shortest basename;
      of those, take the shortest names;
      of those, take the first name.

* The new --binary option makes `patch' read and write files in binary mode.
  This option has no effect on POSIX-compliant hosts;
  it is useful only in on operating systems like DOS
  that distinguish between text and binary I/O.

* The environment variables TMP and TEMP are consulted for the name of
  the temporary directory if TMPDIR is not set.

* A port to MS-DOS and MS-Windows is available; see the `pc' directory.

* Backup file names are no longer ever computed by uppercasing characters,
  since this isn't portable to systems with case-insensitive file names.

Changes in version 2.2:

* Arbitrary limits removed (e.g. line length, file name length).

* On POSIX.1-compliant hosts, you can now patch binary files using the output
  of GNU `diff -a'.

* New options:
  --dry-run
  --help
  --verbose
  -i FILE or --input=FILE
  -y PREF or --basename-prefix=PREF

* patch is now quieter by default; use --verbose for the old chatty behavior.

* Patch now complies better with POSIX.2 if your host complies with POSIX.1.

  Therefore:
  - By default, no backups are made.  Set the VERSION_CONTROL environment
    variable to "existing" if you prefer patch's traditional behavior.
  - The simple backup file name for F defaults to F.orig
    regardless of whether the file system supports long file names,
    and F~ is used only if F.orig is too long for that particular file.
  - Similarly for the reject file names F.rej and F#.

  Also:
  - The pseudo-option `+' has been withdrawn.
  - -b is equivalent to --version-control=simple;
    `-z SUFF' has the meaning that `-b SUFF' used to.
  - Names of files to be patched are taken first from *** line and then from
    --- line of context diffs; then from Index: line; /dev/tty is
    consulted if none of the above files exist.  However, if the patch
    appears to create a file, the file does not have to exist: instead,
    the first name with the longest existing directory prefix is taken.
  - Exit status 0 means success, 1 means hunks were rejected, 2 means trouble.
  - `-l' ignores changes only in spaces and tabs, not in other white space.
  - If no `-p' option is given, `-pINFINITY' is assumed, instead of trying
    to guess the proper value.
  - `-p' now requires an operand; use `-p 0' to get the effect of the old plain
    `-p' option.
  - `-p' treats two or more adjacent slashes as if it were one slash.
  - The TERM signal is caught.
  - New option `-i F' reads patch from F instead of stdin.

* The `patch' options and build procedure conform to current GNU standards.
  For example, the `--version' option now outputs copyright information.

* When the patch is creating a file, but a nonempty file of that name already
  exists, `patch' now asks for confirmation before patching.

* RCS is used only if the version control method is `existing'
  and there is already an RCS file.  Similarly for SCCS.

* Copyright notices have been clarified.  Every file in this version of `patch'
  can be distributed under the GNU General Public License.  See README for
  details.

Changes in version 2.1:

* A few more portability bugs have been fixed.  The version number has
  been changed from 2.0.12g11 to 2.1, because the name
  `patch-2.0.12g10' was too long for traditional Unix file systems.

Versions 2.0.12g9 through 2.0.12g11 fix various portability bugs.

Changes in version 2.0.12g8:

* Start of the 12g series, with a GNU-style configure script and
  long-named options.
* Added the -t --batch option, similar to -f.
* Improved detection of files that are locked under RCS or SCCS.
* Reinstate the -E option to remove output files that are empty after
  being patched.
* Print the system error message when system calls fail.
* Fixed various bugs and portability problems.