Managing multiple patches for a source file

[Seth McDonald]

Hi all,

Following the MacPorts guide on patching source code (see [0], section
4.6.2), it encourages using separate patchfiles for each logical change
and says to diff against the original file.

Given this, I'd like to ask what the about the situation in which
multiple logical changes need to be applied to the same source file.
Since each change may alter the line count of the file, I worry that
just diffing each change against the original file may cause later
patches to not apply due to the expected line numbers being changed.

I can think of three ways this can be managed:

(0) Keep all changes to the same source file within the same patchfile.
This way the problem never occurs, but removes the benefit of logically
separate patches.

(1) Diff each change against the original file.  Perhaps I'm wrong and
MacPorts is actually smart enough to handle sequential patches which
each alter line numbers without the patchfiles accounting for it.

(2) Diff each change against the previous change.  This defines an order
in which the patchfiles must be applied.  This option makes the most
sense in my head.

Is one of these three methods the "correct" way in which multiple
patches should be managed?

Take care,
	Seth McDonald.

[0] <https://guide.macports.org/chunked/development.patches.html>

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