tests/test-merge-revert.t

manifest: document return type of readfast()

I keep having to ponder out what readfast() means, and it always
surprises me. Document the return type in the docstring so that future
readers won't have to puzzle this out again.

  $ hg init

  $ echo "added file1" > file1
  $ echo "added file2" > file2
  $ hg add file1 file2
  $ hg commit -m "added file1 and file2"

  $ echo "changed file1" >> file1
  $ hg commit -m "changed file1"

  $ hg -q log
  1:08a16e8e4408
  0:d29c767a4b52
  $ hg id
  08a16e8e4408 tip

  $ hg update -C 0
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg id
  d29c767a4b52
  $ echo "changed file1" >> file1
  $ hg id
  d29c767a4b52+

  $ hg revert --all
  reverting file1
  $ hg diff
  $ hg status
  ? file1.orig
  $ hg id
  d29c767a4b52

  $ hg update
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg diff
  $ hg status
  ? file1.orig
  $ hg id
  08a16e8e4408 tip

  $ hg update -C 0
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ echo "changed file1" >> file1

  $ hg update
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg diff
  $ hg status
  ? file1.orig
  $ hg id
  08a16e8e4408 tip

  $ hg revert --all
  $ hg diff
  $ hg status
  ? file1.orig
  $ hg id
  08a16e8e4408 tip

  $ hg revert -r tip --all
  $ hg diff
  $ hg status
  ? file1.orig
  $ hg id
  08a16e8e4408 tip

  $ hg update -C
  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg diff
  $ hg status
  ? file1.orig
  $ hg id
  08a16e8e4408 tip