Now that the 'vfs' classes moved in their own module, lets use the new module
directly. We update code iteratively to help with possible bisect needs in the
future.
Previously, two changes that were nearly, but not quite, identical would result
in large merge conflict regions that looked very similar, and were thus very
confusing to users, and lead people used to other source control systems to
claim that "mercurial's merge algorithms suck". In the relatively common case
of a new file being introduced in two branches with very slight modifications,
the old behavior would show the entire file as a conflict, and it would be very
difficult for a user to determine what was going on.
In the past, mercurial attempted to solve this with a "very smart" algorithm
that would find all common lines, but this has significant problems as
described in 3d22d20aa950.
Instead, we use a "very dumb" algorithm introduced in the previous patch that
simply matches lines at the periphery of conflict regions. This minimizes most
conflict regions well, though there may still be some degenerate edge cases,
like small modification to the beginning and end of a large file.
The current output for a failed merge with conflict markers looks something like:
merging foo
warning: conflicts during merge.
merging foo incomplete! (edit conflicts, then use 'hg resolve --mark')
merging bar
warning: conflicts during merge.
merging bar incomplete! (edit conflicts, then use 'hg resolve --mark')
We're going to change the way merges are done to perform all premerges before
all merges, so that the output above would look like:
merging foo
merging bar
warning: conflicts during merge.
merging foo incomplete! (edit conflicts, then use 'hg resolve --mark')
warning: conflicts during merge.
merging bar incomplete! (edit conflicts, then use 'hg resolve --mark')
The 'warning: conflicts during merge' line has no context, so is pretty
confusing.
This patch will change the future output to:
merging foo
merging bar
warning: conflicts while merging foo! (edit, then use 'hg resolve --mark')
warning: conflicts while merging bar! (edit, then use 'hg resolve --mark')
The hint on how to resolve the conflicts makes this a bit unwieldy, but solving
that is tricky because we already hint that people run 'hg resolve' to retry
unresolved merges. The 'hg resolve --mark' mostly applies to conflict marker
based resolution.
The home of 'Abort' is 'error' not 'util' however, a lot of code seems to be
confused about that and gives all the credit to 'util' instead of the
hardworking 'error'. In a spirit of equity, we break the cycle of injustice and
give back to 'error' the respect it deserves. And screw that 'util' poser.
For great justice.
This is a step toward adding 'union merge' to the internal merge tool.
'union merge' is a merge strategy which adds both left and right hand side
of a conflict region. Git implements this merge strategy which is very
practical to have for merging to e.g. the Changelog file.
Note: the identifiers with underscores in this commit are all using existing
variable names and/or keyword arguments.
The following functions in simplemerge are dead code. I reran "make
test-merge*" after this change, and it passed. Looks like cruft that
we've been carrying since we nabbed this code from bzr.
If a third label is provided it will be used for the "base" content:
<<<<<<< local
content
from
local
||||||| base
former
common
=======
other
conflicting
>>>>>>> other
Matt Mackall said:
The goal of simplemerge should have always been to be a drop-in
replacement for RCS merge. Please nuke this minimization thing entirely.
This whole things is now dead.
simplemerge was using list.pop() to remove items from the labels list. This
mutated the list and made it unusable by other calls (for instance, it might be
used in both the premerge and actual merge stages).
The GPLv3 FAQ suggests to upgrade by
[...] replace all your existing v2 license notices (usually at the
top of each file) with the new recommended text available on the GNU
licenses howto. It's more future-proof because it no longer includes
the FSF's postal mailing address.
This removes the postal address, but leaves the version number at 2+.
The usual contract is that close() makes your writes permanent, so
atomictempfile's use of close() to *discard* writes (and rename() to
keep them) is rather unexpected. Thus, change it so close() makes
things permanent and add a new discard() method to throw them away.
discard() is only used internally, in __del__(), to ensure that writes
are discarded when an atomictempfile object goes out of scope.
I audited mercurial.*, hgext.*, and ~80 third-party extensions, and
found no one using the existing semantics of close() to discard
writes, so this should be safe.
When used as the default merge tool, or used as a --tool override,
the simplemerge script should not be allowed to raise a util.Abort
just because one of the files being merged is binary. Instead, return
1 and mark the file unresolved.
