formatter: extract function that encode values to json string
This is the stub for tuple support, which will be used to encode ctx.date()
in the same manner as jsonchangeset printer.
Test for changeset ba7c74081861
(update dirstate correctly for non-branchmerge updates)
$ hg init a
$ cd a
$ echo a > a
$ hg add a
$ hg commit -m a
$ cd ..
$ hg clone a b
updating to branch default
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ cd a
$ hg mv a b
$ hg commit -m move
$ echo b >> b
$ hg commit -m b
$ cd ../b
$ hg pull ../a
pulling from ../a
searching for changes
adding changesets
adding manifests
adding file changes
added 2 changesets with 2 changes to 1 files
(run 'hg update' to get a working copy)
$ hg update
1 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ cd ..