phabricator: rework phabread to reduce memory usage and round-trips
This patch reworked phabread a bit so it fetches the lightweight
"Differential Revision" metadata for a stack first. Then read other data.
This allows the code to:
a) send 1 request to get all `hg:meta` data instead of N requests
b) patches are read in desired order, no need to buffer the output
"b)" reduces the memory usage from O(N^2) to O(N) since we no longer keep
old patch contents in memory.
The above `N` means the number of patches in the stack.
https://bz.mercurial-scm.org/1089
$ hg init
$ mkdir a
$ echo a > a/b
$ hg ci -Am m
adding a/b
$ hg rm a
removing a/b (glob)
$ hg ci -m m a
$ mkdir a b
$ echo a > a/b
$ hg ci -Am m
adding a/b
$ hg rm a
removing a/b (glob)
$ cd b
Relative delete:
$ hg ci -m m ../a
$ cd ..