gendoc: refactor get_cmd
Refactors the get_cmd to take the table as argument, instad
of just referencing the global table, thereby enabling reuse
for extension command tables.
Test update logic when there are renames
Update with local changes across a file rename
$ hg init
$ echo a > a
$ hg add a
$ hg ci -m a
$ hg mv a b
$ hg ci -m rename
$ echo b > b
$ hg ci -m change
$ hg up -q 0
$ echo c > a
$ hg up
merging a and b to b
warning: conflicts during merge.
merging b failed!
0 files updated, 0 files merged, 0 files removed, 1 files unresolved
use 'hg resolve' to retry unresolved file merges
[1]
$ cd ..