--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/tests/testlib/merge-combination-util.sh	Thu Jan 14 11:33:09 2021 +0100
@@ -0,0 +1,73 @@
+# genmerges is the workhorse of the test-merge-combination.t tests.
+
+# Given:
+# - a `range` function describing the possible values for file a
+# - a `isgood` function to filter out uninteresting combination
+# - a `createfile` function to actually write the values for file a on the
+#   filesystem
+#
+# it print a series of lines that look like: abcd C: output of -T {files}
+# describing the file a at respectively the base, p2, p1, merge
+# revision. "C" indicates that hg merge had conflicts.
+
+genmerges () {
+
+  (LC_ALL=C type range | grep -q 'function') || (echo >&2 "missing function: range")
+  (LC_ALL=C type isgood | grep -q 'function') || (echo >&2 "missing function: isgood")
+  (LC_ALL=C type createfile | grep -q 'function') || (echo >&2 "missing function: createfile")
+
+  for base in `range` -; do
+    for r1 in `range $base` -; do
+      for r2 in `range $base $r1` -; do
+        for m in `range $base $r1 $r2` -; do
+          line="$base$r1$r2$m"
+          isgood $line || continue
+          hg init repo
+          cd repo
+          make_commit () {
+            v=$1; msg=$2; file=$3;
+            if [ $v != - ]; then
+              createfile $v
+            else
+              if [ -f a ]
+              then rm a
+              else touch $file
+              fi
+            fi
+            hg commit -q -Am $msg || exit 123
+          }
+          echo foo > foo
+          make_commit $base base b
+          make_commit $r1 r1 c
+          hg up -r 0 -q
+          make_commit $r2 r2 d
+          hg merge -q -r 1 > ../output 2>&1
+          if [ $? -ne 0 ]; then rm -f *.orig; hg resolve -m --all -q; fi
+          if [ -s ../output ]; then conflicts=" C"; else conflicts="  "; fi
+          make_commit $m m e
+          if [ $m = $r1 ] && [ $m = $r2 ]
+          then expected=
+          elif [ $m = $r1 ]
+          then if [ $base = $r2 ]
+               then expected=
+               else expected=a
+               fi
+          elif [ $m = $r2 ]
+          then if [ $base = $r1 ]
+               then expected=
+               else expected=a
+               fi
+          else expected=a
+          fi
+          got=`hg log -r 3 --template '{files}\n' | tr -d 'e '`
+          if [ "$got" = "$expected" ]
+          then echo "$line$conflicts: agree on \"$got\""
+          else echo "$line$conflicts: hg said \"$got\", expected \"$expected\""
+          fi
+          cd ../
+          rm -rf repo
+        done
+      done
+    done
+  done
+}