largefiles: don't allow corruption to propagate after detection
basestore.get uses util.atomictempfile when checking and receiving a new
largefile ... but the close/discard logic was too clever for largefiles.
Largefiles relied on being able to discard the file and thus prevent it from
being written to the store. That was however too brittle. lfutil.copyandhash
closes the infile after writing to it ... with a 'blecch' comment. The discard
was thus a silent noop, and as a result of that corruption would be detected
... and then the corrupted files would be used anyway.
Instead we now use a tmp file and rename or unlink it after validating it.
A better solution should be implemented ... but not now.
http://mercurial.selenic.com/bts/issue612
$ hg init
$ mkdir src
$ echo a > src/a.c
$ hg ci -Ama
adding src/a.c
$ hg mv src source
moving src/a.c to source/a.c (glob)
$ hg ci -Ammove
$ hg co -C 0
1 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ echo new > src/a.c
$ echo compiled > src/a.o
$ hg ci -mupdate
created new head
$ hg status
? src/a.o
$ hg merge
merging src/a.c and source/a.c to source/a.c
0 files updated, 1 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ hg status
M source/a.c
R src/a.c
? src/a.o