--- a/mercurial/helptext/environment.txt	Sat Jan 18 10:37:14 2020 -0800
+++ b/mercurial/helptext/environment.txt	Tue Jan 07 11:24:05 2020 +0100
@@ -49,6 +49,9 @@
     - if it's a directory, all files ending with .rc are added
     - otherwise, the file itself will be added
 
+HGRCSKIPREPO
+    When set, the .hg/hgrc from repositories are not read.
+
 HGPLAIN
     When set, this disables any configuration settings that might
     change Mercurial's default output. This includes encoding,

--- a/mercurial/helptext/scripting.txt	Sat Jan 18 10:37:14 2020 -0800
+++ b/mercurial/helptext/scripting.txt	Tue Jan 07 11:24:05 2020 +0100
@@ -74,6 +74,14 @@
     like the username and extensions that may be required to interface
     with a repository.
 
+HGRCSKIPREPO
+    When set, the .hg/hgrc from repositories are not read.
+
+    Note that not reading the repository's configuration can have
+    unintended consequences, as the repository config files can define
+    things like extensions that are required for access to the
+    repository.
+
 Command-line Flags
 ==================
 

--- a/mercurial/localrepo.py	Sat Jan 18 10:37:14 2020 -0800
+++ b/mercurial/localrepo.py	Tue Jan 07 11:24:05 2020 +0100
@@ -676,6 +676,8 @@
     configs are loaded. For example, an extension may wish to pull in
     configs from alternate files or sources.
     """
+    if b'HGRCSKIPREPO' in encoding.environ:
+        return False
     try:
         ui.readconfig(hgvfs.join(b'hgrc'), root=wdirvfs.base)
         return True

--- a/tests/test-hgrc.t	Sat Jan 18 10:37:14 2020 -0800
+++ b/tests/test-hgrc.t	Tue Jan 07 11:24:05 2020 +0100
@@ -258,3 +258,16 @@
   plain: True
   read config from: $TESTTMP/hgrc
   $TESTTMP/hgrc:17: paths.foo=$TESTTMP/bar
+
+Test we can skip the user configuration
+
+  $ cat >> .hg/hgrc <<EOF
+  > [paths]
+  > elephant = babar
+  > EOF
+  $ hg path
+  elephant = $TESTTMP/babar
+  foo = $TESTTMP/bar
+  $ HGRCSKIPREPO=1 hg path
+  foo = $TESTTMP/bar
+