filemerge: add configs to disable some or all partial merge tools

When rolling out partial merge tools to users, it's useful to be able
to easily turn one or all of them off if a problem is discovered. This
patch adds support for that. They can of course also be useful for
individual users to be able to temporarily turn off a tool they are
otherwise using.

Differential Revision: https://phab.mercurial-scm.org/D12588

mercurial/configitems.py

@@ -1570,6 +1570,12 b' coreconfigitem('
     default=False,
 )
 coreconfigitem(
+    b'merge',
+    b'disable-partial-tools',
+    default=False,
+    experimental=True,
+)
+coreconfigitem(
     b'partial-merge-tools',
     b'.*',
     default=None,
@@ -1609,6 +1615,14 b' coreconfigitem('
     experimental=True,
 )
 coreconfigitem(
+    b'partial-merge-tools',
+    br'.*\.disable',
+    default=False,
+    generic=True,
+    priority=-1,
+    experimental=True,
+)
+coreconfigitem(
     b'merge-tools',
     b'.*',
     default=None,

mercurial/filemerge.py

@@ -1119,6 +1119,8 b' def filemerge(repo, wctx, mynode, orig, '
 def _run_partial_resolution_tools(repo, local, other, base):
     """Runs partial-resolution tools on the three inputs and updates them."""
     ui = repo.ui
+    if ui.configbool(b'merge', b'disable-partial-tools'):
+        return
     # Tuples of (order, name, executable path, args)
     tools = []
     seen = set()
@@ -1133,6 +1135,8 b' def _run_partial_resolution_tools(repo, '
             m = match.match(repo.root, b'', patterns)
             is_match = m(local.fctx.path())
         if is_match:
+            if ui.configbool(section, b'%s.disable' % name):
+                continue
             order = ui.configint(section, b'%s.order' % name, 0)
             executable = ui.config(section, b'%s.executable' % name, name)
             args = ui.config(section, b'%s.args' % name)

tests/test-merge-partial-tool.t

@@ -120,6 +120,57 b' be recorded and the regular merge tool s'
   e
 
 
+Can disable all partial merge tools (the `head` tool would have resolved this
+conflict it had been enabled)
+
+  $ hg up -C 4
+  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  $ hg merge 3 -t :merge3 --config merge.disable-partial-tools=yes
+  merging file
+  warning: conflicts while merging file! (edit, then use 'hg resolve --mark')
+  0 files updated, 0 files merged, 0 files removed, 1 files unresolved
+  use 'hg resolve' to retry unresolved file merges or 'hg merge --abort' to abandon
+  [1]
+  $ cat file
+  a
+  b
+  c
+  d
+  e
+  <<<<<<< working copy:    d57edaa6e21a - test: a b c d e f3
+  f3
+  ||||||| common ancestor: 8ae8bb9cc43a - test: a b c d e f
+  f
+  =======
+  f2
+  >>>>>>> merge rev:       8c217da987be - test: a b c d e f2
+
+
+Can disable one partial merge tool (the `head` tool would have resolved this
+conflict it had been enabled)
+
+  $ hg up -C 4
+  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  $ hg merge 3 -t :merge3 --config partial-merge-tools.head.disable=yes
+  merging file
+  warning: conflicts while merging file! (edit, then use 'hg resolve --mark')
+  0 files updated, 0 files merged, 0 files removed, 1 files unresolved
+  use 'hg resolve' to retry unresolved file merges or 'hg merge --abort' to abandon
+  [1]
+  $ cat file
+  b
+  c
+  d
+  e
+  <<<<<<< working copy:    d57edaa6e21a - test: a b c d e f3
+  f3
+  ||||||| common ancestor: 8ae8bb9cc43a - test: a b c d e f
+  f
+  =======
+  f2
+  >>>>>>> merge rev:       8c217da987be - test: a b c d e f2
+
+
 Only tools whose patterns match are run. We make `head` not match here, so
 only `tail` should run