simplemerge: make minimize() a free function

IMO, `Merge3Text` should be about merging text without knowing about
conflict markers. "Conflict minimization" is about making conflict
markers smaller, so it should be moved out. This patch does that. I'll
refactor it next.

Differential Revision: https://phab.mercurial-scm.org/D11980

mercurial/simplemerge.py

@@ -214,50 +214,6 b' class Merge3Text(object):'
                 ia = aend
                 ib = bend
 
-    def minimize(self, merge_groups):
-        """Trim conflict regions of lines where A and B sides match.
-
-        Lines where both A and B have made the same changes at the beginning
-        or the end of each merge region are eliminated from the conflict
-        region and are instead considered the same.
-        """
-        for what, lines in merge_groups:
-            if what != b"conflict":
-                yield what, lines
-                continue
-            base_lines, a_lines, b_lines = lines
-            alen = len(a_lines)
-            blen = len(b_lines)
-
-            # find matches at the front
-            ii = 0
-            while ii < alen and ii < blen and a_lines[ii] == b_lines[ii]:
-                ii += 1
-            startmatches = ii
-
-            # find matches at the end
-            ii = 0
-            while (
-                ii < alen and ii < blen and a_lines[-ii - 1] == b_lines[-ii - 1]
-            ):
-                ii += 1
-            endmatches = ii
-
-            if startmatches > 0:
-                yield b'same', a_lines[:startmatches]
-
-            yield (
-                b'conflict',
-                (
-                    base_lines,
-                    a_lines[startmatches : alen - endmatches],
-                    b_lines[startmatches : blen - endmatches],
-                ),
-            )
-
-            if endmatches > 0:
-                yield b'same', a_lines[alen - endmatches :]
-
     def find_sync_regions(self):
         """Return a list of sync regions, where both descendants match the base.
 
@@ -350,6 +306,49 b' def _detect_newline(m3):'
     return b'\n'
 
 
+def _minimize(merge_groups):
+    """Trim conflict regions of lines where A and B sides match.
+
+    Lines where both A and B have made the same changes at the beginning
+    or the end of each merge region are eliminated from the conflict
+    region and are instead considered the same.
+    """
+    for what, lines in merge_groups:
+        if what != b"conflict":
+            yield what, lines
+            continue
+        base_lines, a_lines, b_lines = lines
+        alen = len(a_lines)
+        blen = len(b_lines)
+
+        # find matches at the front
+        ii = 0
+        while ii < alen and ii < blen and a_lines[ii] == b_lines[ii]:
+            ii += 1
+        startmatches = ii
+
+        # find matches at the end
+        ii = 0
+        while ii < alen and ii < blen and a_lines[-ii - 1] == b_lines[-ii - 1]:
+            ii += 1
+        endmatches = ii
+
+        if startmatches > 0:
+            yield b'same', a_lines[:startmatches]
+
+        yield (
+            b'conflict',
+            (
+                base_lines,
+                a_lines[startmatches : alen - endmatches],
+                b_lines[startmatches : blen - endmatches],
+            ),
+        )
+
+        if endmatches > 0:
+            yield b'same', a_lines[alen - endmatches :]
+
+
 def render_minimized(
     m3,
     name_a=None,
@@ -366,7 +365,7 b' def render_minimized('
     if name_b:
         end_marker = end_marker + b' ' + name_b
     merge_groups = m3.merge_groups()
-    merge_groups = m3.minimize(merge_groups)
+    merge_groups = _minimize(merge_groups)
     lines = []
     for what, group_lines in merge_groups:
         if what == b'conflict':