view README @ 26752:949e8c626d19

merge: make in-memory changes visible to external update hooks

51844b8b5017 (while 3.4 code-freeze) made all 'update' hooks run after
releasing wlock for visibility of in-memory dirstate changes. But this
breaks paired invocation of 'preupdate' and 'update' hooks.

For example, 'hg backout --merge' for TARGET revision, which isn't
parent of CURRENT, consists of steps below:

  1. update from CURRENT to TARGET
  2. commit BACKOUT revision, which backs TARGET out
  3. update from BACKOUT to CURRENT
  4. merge TARGET into CURRENT

Then, we expects hooks to run in the order below:

  - 'preupdate' on CURRENT for (1)
  - 'update'    on TARGET  for (1)
  - 'preupdate' on BACKOUT for (3)
  - 'update'    on CURRENT for (3)
  - 'preupdate' on TARGET  for (4)
  - 'update'    on CURRENT/TARGET for (4)

But hooks actually run in the order below:

  - 'preupdate' on CURRENT for (1)
  - 'preupdate' on BACKOUT for (3)
  - 'preupdate' on TARGET  for (4)
  - 'update'    on TARGET  for (1), but actually on CURRENT/TARGET
  - 'update'    on CURRENT for (3), but actually on CURRENT/TARGET
  - 'update'    on CURRENT for (4), but actually on CURRENT/TARGET

Root cause of the issue focused by 51844b8b5017 is that external
'update' hook process can't view in-memory changes (especially, of
dirstate), because they aren't written out until the end of
transaction (or wlock).

Now, hooks can be invoked just after updating, because previous
patches made in-memory changes visible to external process.

This patch may break backward compatibility from the point of view of
"scheduling hook execution", but should be reasonable because 'update'
hooks had been executed in this order before 3.4.

This patch tests "hg backout" and "hg unshelve", because the former
activates the transaction before 'update' hook invocation, but the
former doesn't.

Mercurial
=========

Mercurial is a fast, easy to use, distributed revision control tool
for software developers.

Basic install:

 $ make            # see install targets
 $ make install    # do a system-wide install
 $ hg debuginstall # sanity-check setup
 $ hg              # see help

Running without installing:

 $ make local      # build for inplace usage
 $ ./hg --version  # should show the latest version

See https://mercurial-scm.org/ for detailed installation
instructions, platform-specific notes, and Mercurial user information.