tests/test-diffdir.t

test: extract some generic data and utility from test-rust-ancestor.py

We will reuse this for more tests related to revlog index. In pratice this
series of changesets add an index implementation provided from Rust and we want
to be able to test it.

Differential Revision: https://phab.mercurial-scm.org/D7652

  $ hg init
  $ touch a
  $ hg add a
  $ hg ci -m "a"

  $ echo 123 > b
  $ hg add b
  $ hg diff --nodates
  diff -r 3903775176ed b
  --- /dev/null
  +++ b/b
  @@ -0,0 +1,1 @@
  +123

  $ hg diff --nodates -r tip
  diff -r 3903775176ed b
  --- /dev/null
  +++ b/b
  @@ -0,0 +1,1 @@
  +123

  $ echo foo > a
  $ hg diff --nodates
  diff -r 3903775176ed a
  --- a/a
  +++ b/a
  @@ -0,0 +1,1 @@
  +foo
  diff -r 3903775176ed b
  --- /dev/null
  +++ b/b
  @@ -0,0 +1,1 @@
  +123

  $ hg diff -r ""
  hg: parse error: empty query
  [255]
  $ hg diff -r tip -r ""
  hg: parse error: empty query
  [255]

Remove a file that was added via merge. Since the file is not in parent 1,
it should not be in the diff.

  $ hg ci -m 'a=foo' a
  $ hg co -Cq null
  $ echo 123 > b
  $ hg add b
  $ hg ci -m "b"
  created new head
  $ hg merge 1
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg rm -f a
  $ hg diff --nodates

Rename a file that was added via merge. Since the rename source is not in
parent 1, the diff should be relative to /dev/null

  $ hg co -Cq 2
  $ hg merge 1
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg mv a a2
  $ hg diff --nodates
  diff -r cf44b38435e5 a2
  --- /dev/null
  +++ b/a2
  @@ -0,0 +1,1 @@
  +foo
  $ hg diff --nodates --git
  diff --git a/a2 b/a2
  new file mode 100644
  --- /dev/null
  +++ b/a2
  @@ -0,0 +1,1 @@
  +foo