Re: [bug-patch] patch cannot handle >3 lines of context

[Jörn Engel]

Hello Andreas!

On Sat, Jul 18, 2015 at 09:19:27AM +0200, Andreas Grünbacher wrote:
> 2015-07-17 19:49 GMT+02:00 Jörn Engel <address@hidden>:
> > Noticed the problem trying to apply the hunk below.  It applies just
> > fine with git, but fails to apply with GNU patch.  Cutting the 7-line
> > context above the patch down to 3-line context fixes the issue.  Cutting
> > it down to 5-line context makes it apply with fuzz 2.
> 
> The reason is that there are more lines of prefix context than suffix context,
> which makes patch assume that the hunk must apply at the end of the
> file. (Without this heuristic, hunks from the beginning or end of a file
> misapply very easily.)
> 
> Once two lines of a hunk with five prefix context lines and three suffix
> context lines are stripped (fuzz 2), the number of context lines balances
> out again, and the hunk will apply anywhere in the file.

Not sure how to interpret your answer.  Given that git or a human can
apply the patch just find, I would consider it a legal patch.  As such,
I would be unhappy about an answer that implied "there is no bug".  An
answer of "this is hard, send a patch if you care" would be fine.  I had
a brief look at the code and decided to work on something else instead.

I mainly sent this bug report for documentation.  We only get into this
situation when humans hand-edit patches.  In my case I removed a "-"
line between 3-line context and 4-line context.  That is exceedingly
rare, even for crazy people that manually edit patches.

Jörn

--
Unless something dramatically changes, by 2015 we'll be largely
wondering what all the fuss surrounding Linux was really about.
-- Rob Enderle