diffutils: Changed White Space
10.3.1 Applying Patches with Changed White Space
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Sometimes mailers, editors, or other programs change spaces into tabs,
or vice versa. If this happens to a patch file or an input file, the
files might look the same, but ‘patch’ will not be able to match them
properly. If this problem occurs, use the ‘-l’ or
‘--ignore-white-space’ option, which makes ‘patch’ compare blank
characters (i.e. spaces and tabs) loosely so that any nonempty sequence
of blanks in the patch file matches any nonempty sequence of blanks in
the input files. Non-blank characters must still match exactly. Each
line of the context must still match a line in the input file.