tests/test-issue619.t

hgweb: show as same parents as "hg parents -r REV FILE" in pages for file

Before this patch, "parents" in pages for file doesn't show as same
parents as "hg parents -r REV FILE", when the specified file is not
modified in the specified revision.

For example, it is assumed that revision A, B and D change file "f".

    changelog   (A) ---> (B) ---> (C) ---> (D)
    filelog "f" (x) ---> (y) ------------> (z)

"/file/D/f" invokes "webutil.parents()" with filectx(z) gotten from
changectx(D), and it returns changectx(B). This is as same result as
"hg parents -r D f".

In the other hand, "/file/C/f" invokes "webutil.parents()" with
filectx(y') gotten from changectx(C), and it returns changectx(A),
because filectx(y') is linked to changectx(B), and works like
filectx(y) in some cases.

In this case, revision B is hidden from users browsing file "f" in
revision C.

This patch shows as same parents as "hg parents -r REV FILE" in pages
for file, by making "webutil.parents()" return:

  - "linkrev()"-ed revision only, if:

    - specified context instance is "filectx" (because
      "webutil.parents()" is invoked with changectx, too), and

    - (1) the revision from which filectx is gotten and (2) the one to
      which filectx is linked are different from each other

  - revision gotten from "ctx.parents()", otherwise

http://mercurial.selenic.com/bts/issue619

  $ hg init
  $ echo a > a
  $ hg ci -Ama
  adding a

  $ echo b > b
  $ hg branch b
  marked working directory as branch b
  (branches are permanent and global, did you want a bookmark?)
  $ hg ci -Amb
  adding b

  $ hg co -C 0
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved

Fast-forward:

  $ hg merge b
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg ci -Ammerge

Bogus fast-forward should fail:

  $ hg merge b
  abort: merging with a working directory ancestor has no effect
  [255]