# HG changeset patch
# User Anton Shestakov <av6@dwimlabs.net>
# Date 1615287010 -28800
# Node ID 82040a455e71caf61be1e2468322b4ca74df16cb
# Parent  524eb673ac52f5aa88127be040f7041cc85aeb10
evolve: check if in-memory is supported on a good enough level for evolve

diff -r 524eb673ac52 -r 82040a455e71 CHANGELOG
--- a/CHANGELOG	Tue Feb 02 00:05:19 2021 +0530
+++ b/CHANGELOG	Tue Mar 09 18:50:10 2021 +0800
@@ -5,7 +5,7 @@
 --------------------
 
   * evolve: add a experimental.evolution.in-memory config for running evolve
-    in memory
+    in memory (hg >= 5.6)
   * evolve: improve content-divergence resolution that involves parent changes
   * evolve: preserve wdir parent when using `hg evolve --stop`
   * obslog: clarify the command name in the help,
diff -r 524eb673ac52 -r 82040a455e71 hgext3rd/evolve/evolvecmd.py
--- a/hgext3rd/evolve/evolvecmd.py	Tue Feb 02 00:05:19 2021 +0530
+++ b/hgext3rd/evolve/evolvecmd.py	Tue Mar 09 18:50:10 2021 +0800
@@ -918,6 +918,13 @@
     return commitmsg
 
 def use_in_memory_merge(repo):
+    try:
+        from mercurial import mergestate as mergestatemod
+        mergestatemod.memmergestate
+    except (AttributeError, ImportError):
+        # no in-memory evolve if Mercurial lacks the required code
+        # hg <= 5.5 (19590b126764)
+        return False
     config_value = repo.ui.config(b'experimental', b'evolution.in-memory')
     if config_value == b'force':
         return True