tests/test-empty-group.out

patch: support diff data loss detection and upgrade

In worst case, generating diff in upgrade mode can be two times more expensive
than generating it in git mode directly: we may have to regenerate the whole
diff again whenever a git feature is detected. Also, the first diff attempt is
completely buffered instead of being streamed. That said, even without having
profiled it yet, I am convinced we can fast-path the upgrade mode if necessary
were it to be used in regular diff commands, and not only in mq where avoiding
data loss is worth the price.

adding init
adding x
adding y
0 files updated, 0 files merged, 2 files removed, 0 files unresolved
adding x
adding y
created new head
0 files updated, 0 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
0 files updated, 0 files merged, 0 files removed, 0 files unresolved
0 files updated, 0 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
created new head
requesting all changes
adding changesets
adding manifests
adding file changes
added 4 changesets with 3 changes to 3 files
updating to branch default
3 files updated, 0 files merged, 0 files removed, 0 files unresolved
requesting all changes
adding changesets
adding manifests
adding file changes
added 4 changesets with 3 changes to 3 files
updating to branch default
3 files updated, 0 files merged, 0 files removed, 0 files unresolved
comparing with b
searching for changes
changeset:   4:fdb3c546e859
tag:         tip
parent:      1:1f703b3fcbc6
parent:      2:de997049e034
user:        test
date:        Mon Jan 12 13:46:40 1970 +0000
summary:     m2

comparing with c
searching for changes
changeset:   3:f40f830c0024
parent:      2:de997049e034
parent:      1:1f703b3fcbc6
user:        test
date:        Mon Jan 12 13:46:40 1970 +0000
summary:     m1

comparing with c
searching for changes
changeset:   3:f40f830c0024
tag:         tip
parent:      2:de997049e034
parent:      1:1f703b3fcbc6
user:        test
date:        Mon Jan 12 13:46:40 1970 +0000
summary:     m1

comparing with b
searching for changes
changeset:   3:fdb3c546e859
tag:         tip
parent:      1:1f703b3fcbc6
parent:      2:de997049e034
user:        test
date:        Mon Jan 12 13:46:40 1970 +0000
summary:     m2

pulling from a
searching for changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 0 changes to 0 files (+1 heads)
(run 'hg heads' to see heads, 'hg merge' to merge)
pulling from a
searching for changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 0 changes to 0 files (+1 heads)
(run 'hg heads' to see heads, 'hg merge' to merge)