localrepo: introduce a clone_requirements function

localrepo: introduce a clone_requirements function

This function take a source repository and return a relevant set of
requirements that should be used by a copy clone.

This will help make the creation of the destination repository during copy
clone simpler.

Differential Revision: https://phab.mercurial-scm.org/D10849

--- a/mercurial/localrepo.py	Mon Jun 07 20:40:43 2021 +0200
+++ b/mercurial/localrepo.py	Wed Jun 09 01:10:26 2021 +0200
@@ -3485,6 +3485,24 @@
     return createopts
 
 
+def clone_requirements(ui, createopts, srcrepo):
+    """clone the requirements of a local repo for a local clone
+
+    The store requirements are unchanged while the working copy requirements
+    depends on the configuration
+    """
+    target_requirements = set()
+    createopts = defaultcreateopts(ui, createopts=createopts)
+    for r in newreporequirements(ui, createopts):
+        if r in requirementsmod.WORKING_DIR_REQUIREMENTS:
+            target_requirements.add(r)
+
+    for r in srcrepo.requirements:
+        if r not in requirementsmod.WORKING_DIR_REQUIREMENTS:
+            target_requirements.add(r)
+    return target_requirements
+
+
 def newreporequirements(ui, createopts):
     """Determine the set of requirements for a new local repository.