--- a/mercurial/configitems.py	Wed May 04 18:17:44 2022 +0200
+++ b/mercurial/configitems.py	Tue Apr 26 09:06:30 2022 -0700
@@ -1570,6 +1570,12 @@
     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 @@
     experimental=True,
 )
 coreconfigitem(
+    b'partial-merge-tools',
+    br'.*\.disable',
+    default=False,
+    generic=True,
+    priority=-1,
+    experimental=True,
+)
+coreconfigitem(
     b'merge-tools',
     b'.*',
     default=None,

--- a/mercurial/filemerge.py	Wed May 04 18:17:44 2022 +0200
+++ b/mercurial/filemerge.py	Tue Apr 26 09:06:30 2022 -0700
@@ -1119,6 +1119,8 @@
 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 @@
             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)

--- a/tests/test-merge-partial-tool.t	Wed May 04 18:17:44 2022 +0200
+++ b/tests/test-merge-partial-tool.t	Tue Apr 26 09:06:30 2022 -0700
@@ -120,6 +120,57 @@
   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