tests/test-issue1502.t

templater: pass (context, mapping) down to unwraphybrid()

See the subsequent patches for why.

I initially thought it would be wrong to pass a mapping to flatten() and
stringify() since these functions may be applied to a tree of generators,
where each node should be bound to the mapping when it was evaluated. But,
actually that isn't a problem. If an intermediate node has to override a
mapping dict, it can do on unwraphybrid() and yield "unwrapped" generator
of byte strings:

   "{f(g(v))}"  # literal template example.
       ^^^^     # g() want to override a mapping, so it returns a wrapped
                # object 'G{V}' with partial mapping 'lm' attached.
     ^^^^^^^    # f() stringifies 'G{V}', starting from a mapping 'm'.
                # when unwrapping 'G{}', it updates 'm' with 'lm', and
                # passes it to 'V'.

This structure is important for the formatter (and the hgweb) to build a
static template keyword, which can't access a mapping dict until evaluation
phase.

https://bz.mercurial-scm.org/1502

Initialize repository

  $ hg init foo
  $ touch foo/a && hg -R foo commit -A -m "added a"
  adding a

  $ hg clone foo foo1
  updating to branch default
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

  $ echo "bar" > foo1/a && hg -R foo1 commit -m "edit a in foo1"
  $ echo "hi" > foo/a && hg -R foo commit -m "edited a foo"
  $ hg -R foo1 pull
  pulling from $TESTTMP/foo
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files (+1 heads)
  new changesets 273d008d6e8e
  (run 'hg heads' to see heads, 'hg merge' to merge)

  $ hg -R foo1 book branchy
  $ hg -R foo1 book
   * branchy                   1:e3e522925eff

Pull. Bookmark should not jump to new head.

  $ echo "there" >> foo/a && hg -R foo commit -m "edited a again"
  $ hg -R foo1 pull
  pulling from $TESTTMP/foo
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files
  new changesets 84a798d48b17
  (run 'hg update' to get a working copy)

  $ hg -R foo1 book
   * branchy                   1:e3e522925eff