9d158601b3
When looking for a place to apply a hunk, we used to check lines that
match the preimage of it, starting from the line that the patch wants to
apply the hunk at, looking forward and backward with increasing offsets
until we find a match.
Colin Guthrie found an interesting case where this misapplied a patch that
wanted to touch a preimage that consists of
}
}
return 0;
}
which is a rather unfortunately common pattern.
The target version of the file originally had only one such location, but
the hunk immediately before that created another instance of such block of
lines, and find_pos() happily reported that the preimage of the hunk
matched what it wanted to modify.
Oops.
By marking the lines application of earlier hunks touched and preventing
match_fragment() from considering them as a match with preimage of other
hunks, we can reduce such an accident.
I also considered to teach apply_one_fragment() to take the offset we have
found while applying the previous hunk into account when looking for a
match with find_pos(), but dismissed that approach, because it would
sometimes work better but sometimes worse, depending on the difference
between the version the patch was created against and the version the
patch is being applied.
This does _not_ prevent misapplication of patches to a file that has many
similar looking blocks of lines and a preimage cannot identify which one
of them should be applied. For that, we would need to scan beyond the
first match in find_pos(), and issue a warning (or error out). That will
be a separate topic.
Signed-off-by: Junio C Hamano <gitster@pobox.com>
////////////////////////////////////////////////////////////////
GIT - the stupid content tracker
////////////////////////////////////////////////////////////////
"git" can mean anything, depending on your mood.
- random three-letter combination that is pronounceable, and not
actually used by any common UNIX command. The fact that it is a
mispronunciation of "get" may or may not be relevant.
- stupid. contemptible and despicable. simple. Take your pick from the
dictionary of slang.
- "global information tracker": you're in a good mood, and it actually
works for you. Angels sing, and a light suddenly fills the room.
- "goddamn idiotic truckload of sh*t": when it breaks
Git is a fast, scalable, distributed revision control system with an
unusually rich command set that provides both high-level operations
and full access to internals.
Git is an Open Source project covered by the GNU General Public License.
It was originally written by Linus Torvalds with help of a group of
hackers around the net. It is currently maintained by Junio C Hamano.
Please read the file INSTALL for installation instructions.
See Documentation/gittutorial.txt to get started, then see
Documentation/everyday.txt for a useful minimum set of commands, and
Documentation/git-commandname.txt for documentation of each command.
If git has been correctly installed, then the tutorial can also be
read with "man gittutorial" or "git help tutorial", and the
documentation of each command with "man git-commandname" or "git help
commandname".
CVS users may also want to read Documentation/gitcvs-migration.txt
("man gitcvs-migration" or "git help cvs-migration" if git is
installed).
Many Git online resources are accessible from http://git-scm.com/
including full documentation and Git related tools.
The user discussion and development of Git take place on the Git
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The messages titled "A note from the maintainer", "What's in
git.git (stable)" and "What's cooking in git.git (topics)" and
the discussion following them on the mailing list give a good
reference for project status, development direction and
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