In the next commit, we will make it possible for blank context
lines to match beyond the end of the file. That means that a hunk
with a preimage that has more lines than present in the file may
be possible to successfully apply. Therefore, we must remove
the quick rejection test in find_pos().
find_pos() will already work correctly without the quick
rejection test, but that might not be obvious. Therefore,
comment the test for handling out-of-range line numbers in
find_pos() and cast the "line" variable to the same (unsigned)
type as img->nr.
What are performance implications of removing the quick
rejection test?
It can only help "git apply" to reject a patch faster. For example,
if I have a file with one million lines and a patch that removes
slightly more than 50 percent of the lines and try to apply that
patch twice, the second attempt will fail slightly faster
with the test than without (based on actual measurements).
However, there is the pathological case of a patch with many
more context lines than the default three, and applying that patch
using "git apply -C1". Without the rejection test, the running
time will be roughly proportional to the number of context lines
times the size of the file. That could be handled by writing
a more complicated rejection test (it would have to count the
number of blanks at the end of the preimage), but I don't find
that worth doing until there is a real-world use case that
would benfit from it.
It would be possible to keep the quick rejection test if
--whitespace=fix is not given, but I don't like that from
a testing point of view.
Signed-off-by: Björn Gustavsson <bgustavsson@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Even after a handfle attempts, match_beginning logic still has corner
cases:
1bf1a85 (apply: treat EOF as proper context., 2006-05-23)
65aadb9 (apply: force matching at the beginning., 2006-05-24)
4be6096 (apply --unidiff-zero: loosen sanity checks ..., 2006-09-17)
ee5a317 (Fix "git apply" to correctly enforce "match ..., 2008-04-06)
This is a tricky piece of code.
We still incorrectly enforce "match_beginning" for -U0 matches.
I noticed this while trying out an example sequence from Clemens Buchacher:
$ echo a >victim
$ git add victim
$ echo b >>victim
$ git diff -U0 >patch
$ cat patch
diff --git i/victim w/victim
index 7898192..422c2b7 100644
--- i/victim
+++ w/victim
@@ -1,0 +2 @@ a
+b
$ git apply --cached --unidiff-zero <patch
$ git show :victim
b
a
The change inserts a new line before the second line, but we insist it to
be applied at the beginning. As the result, the code refuses to apply it
at the original offset, and we end up adding the line at the beginning.
Updates to the test script are by Clemens Buchacher.
Signed-off-by: Junio C Hamano <gitster@pobox.com>
As a general principle, we should not use "git diff" to validate the
results of what git command that is being tested has done. We would not
know if we are testing the command in question, or locating a bug in the
cute hack of "git diff --no-index".
Rather use test_cmp for that purpose.
Signed-off-by: Junio C Hamano <gitster@pobox.com>
An earlier commit 4be6096 (apply --unidiff-zero: loosen sanity checks for
--unidiff=0 patches, 2006-09-17) made match_beginning and match_end
computed incorrectly. If a hunk inserts at the beginning, old position
recorded at the hunk is line 0, and if a hunk changes at the beginning, it
is line 1. The new test added to t4104 exposes that the old code did not
insist on matching at the beginning for a patch to add a line to an empty
file.
An even older 65aadb9 (apply: force matching at the beginning.,
2006-05-24) was equally wrong in that it tried to take hints from the
number of leading context lines, to decide if the hunk must match at the
beginning, but we can just look at the line number in the hunk to decide.
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Now that "git diff" handles stdin and relative paths outside the
working tree correctly, we can convert all instances of "diff -u"
to "git diff".
This commit is really the result of
$ perl -pi.bak -e 's/diff -u/git diff/' $(git grep -l "diff -u" t/)
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <junkio@cox.net>
(cherry picked from commit c699a40d68215c7e44a5b26117a35c8a56fbd387)
In "git-apply", we have a few sanity checks and heuristics that
expects that the patch fed to us is a unified diff with at least
one line of context.
* When there is no leading context line in a hunk, the hunk
must apply at the beginning of the preimage. Similarly, no
trailing context means that the hunk is anchored at the end.
* We learn a patch deletes the file from a hunk that has no
resulting line (i.e. all lines are prefixed with '-') if it
has not otherwise been known if the patch deletes the file.
Similarly, no old line means the file is being created.
And we declare an error condition when the file created by a
creation patch already exists, and/or when a deletion patch
still leaves content in the file.
These sanity checks are good safety measures, but breaks down
when people feed a diff generated with --unified=0. This was
recently noticed first by Matthew Wilcox and Gerrit Pape.
This adds a new flag, --unified-zero, to allow bypassing these
checks. If you are in control of the patch generation process,
you should not use --unified=0 patch and fix it up with this
flag; rather you should try work with a patch with context. But
if all you have to work with is a patch without context, this
flag may come handy as the last resort.
Signed-off-by: Junio C Hamano <junkio@cox.net>
