ediff: Patch and Diff Programs
7.8 Patch and Diff Programs
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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-diff-program’
‘ediff-diff3-program’
These variables specify the programs to use to produce differences
and do patching.
‘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-coding-system-for-read’
This variable specifies the coding system to use when reading the
output that the programs ‘diff3’ and ‘diff’ send to Emacs. The
default is ‘raw-text’, and this should work fine in Unix and in
most cases under Windows NT/95/98/2000. There are ‘diff’ programs
for which the default option doesn’t work under Windows. In such
cases, ‘raw-text-dos’ might work. If not, you will have to
experiment with other coding systems or use GNU diff.
‘ediff-patch-program’
The program to use to apply patches. Since there are certain
incompatibilities between the different versions of the patch
program, the best way to stay out of trouble is to use a
GNU-compatible version. Otherwise, you may have to tune the values
of the variables ‘ediff-patch-options’, ‘ediff-backup-specs’, and
‘ediff-backup-extension’ as described below.
‘ediff-patch-options’
Options to pass to ‘ediff-patch-program’.
Note: the ‘-b’ and ‘-z’ options should be specified in
‘ediff-backup-specs’, not in ‘ediff-patch-options’.
It is recommended to pass the ‘-f’ option to the patch program, so
it won’t ask questions. However, some implementations don’t accept
this option, in which case the default value of this variable
should be changed.
‘ediff-backup-extension’
Backup extension used by the patch program. Must be specified,
even if ‘ediff-backup-specs’ is given.
‘ediff-backup-specs’
Backup directives to pass to the patch program. Ediff requires
that the old version of the file (before applying the patch) is
saved in a file named ‘the-patch-file.EXTENSION’. Usually
EXTENSION is ‘.orig’, but this can be changed by the user, and may
also be system-dependent. Therefore, Ediff needs to know the
backup extension used by the patch program.
Some versions of the patch program let the user specify ‘-b
EXTENSION’ to specify a backup file name extension. Other versions
only permit ‘-b’, which (usually) assumes the extension ‘.orig’.
Yet others force you to use ‘-zEXTENSION’.
Both ‘ediff-backup-extension’ and EDIFF-BACKUP-SPECS must be
properly set. If your patch program takes the option ‘-b’, but not
‘-b EXTENSION’, the variable ‘ediff-backup-extension’ must still be
set so Ediff will know which extension to use.
‘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.
Info Catalog
ediff: Refinement of Difference Regions
ediff: Customization
ediff: Merging and diff3