RFC: external tool to answer merge prompts (and others?)

[Thomas Arendsen Hein]

Hi!

In some situations the user will be prompted for decisions during
merge, e.g.:

 "local changed %s which remote deleted
  use (c)hanged version or (d)elete?"

To be able to automate giving non-default answers or use an external
GUI tool when using frontends, a mechanism similar to the current
[merge-tools] section could be created.

Configuration could look like this:

  [merge-prompts]
  internal:prompt.priority=0
  internal:prompt.interactive=False
  internal:prompt.label=remote-changed-local-deleted

  tool1.priority=10
  tool1.interactive=False
  tool1.label=local-changed-remote-deleted

  tool2.priority=20
  tool2.executable = /path/to/tool2
  #tool2.regkey = Software\FooSoftware\PromptThingy
  tool2.args=$msg $choices $default $base $local $other $file
  tool2.gui=True
  tool2.interactive=True
  tool2.label=local-changed-remote-deleted, remote-changed-local-deleted

With the first block (internal:prompt) you could automatically give
the default answer (or internal:prompt.choice=1 to choose the second
option).

tool1 would be an automatic script that reads environment variables
to make a decision: $HG_FILE, $HG_OTHER_NODE, $HG_MY_NODE,
$HG_BASE_NODE (same as currently with [merge-tools])

tool2 would open an interactive GUI to let the user decide what to
do, using arguments instead of environment variables.
TortoiseHG already does something like this by overriding
ui.promptchoice, but e.g. MercurialEclipse always uses the default
answer.


I limited this to the ui.promptchoice calls done during merge, so
this matches the existing [merge-tools] configuration and to make it
cooperate with existing TortoiseHG code.

Of course this mechanism could be implemented for any calls to
ui.prompt or ui.promptchoice, in which case the label check for
merges could be something like:
  tool1.label="merge.local-changed-remote-deleted"
or for a more generic merge-prompt tool:
  tool1.label="merge.*"


Thoughts?

Regards,
Thomas

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