1 files changed, 132 insertions, 0 deletions
diff --git a/bin/merge-driver-ekeyword b/bin/merge-driver-ekeyword
new file mode 100755
index 0000000..2df83fc
--- /dev/null
+++ b/bin/merge-driver-ekeyword
@@ -0,0 +1,132 @@
+#!/usr/bin/python
+#
+# Copyright 2020 Gentoo Authors
+# Distributed under the terms of the GNU General Public License v2 or later
+
+"""
+Custom git merge driver for handling conflicts in KEYWORDS assignments
+
+See https://git-scm.com/docs/gitattributes#_defining_a_custom_merge_driver
+"""
+
+import difflib
+import os
+import sys
+import tempfile
+
+from typing import List, Optional, Tuple
+
+from gentoolkit.ekeyword import ekeyword
+
+
+def keyword_array(keyword_line: str) -> List[str]:
+    # Find indices of string inside the double-quotes
+    i1: int = keyword_line.find('"') + 1
+    i2: int = keyword_line.rfind('"')
+
+    # Split into array of KEYWORDS
+    return keyword_line[i1:i2].split(' ')
+
+
+def keyword_line_changes(old: str, new: str) -> List[Tuple[Optional[str],
+                                                           Optional[str]]]:
+    a: List[str] = keyword_array(old)
+    b: List[str] = keyword_array(new)
+
+    s = difflib.SequenceMatcher(a=a, b=b)
+
+    changes = []
+    for tag, i1, i2, j1, j2 in s.get_opcodes():
+        if tag == 'replace':
+            changes.append((a[i1:i2], b[j1:j2]),)
+        elif tag == 'delete':
+            changes.append((a[i1:i2], None),)
+        elif tag == 'insert':
+            changes.append((None, b[j1:j2]),)
+        else:
+            assert tag == 'equal'
+    return changes
+
+
+def keyword_changes(ebuild1: str, ebuild2: str) -> List[Tuple[Optional[str],
+                                                              Optional[str]]]:
+    with open(ebuild1) as e1, open(ebuild2) as e2:
+        lines1 = e1.readlines()
+        lines2 = e2.readlines()
+
+        diff = difflib.unified_diff(lines1, lines2, n=0)
+        assert next(diff) == '--- \n'
+        assert next(diff) == '+++ \n'
+
+        hunk: int = 0
+        old: str = ''
+        new: str = ''
+
+        for line in diff:
+            if line.startswith('@@ '):
+                if hunk > 0:
+                    break
+                hunk += 1
+            elif line.startswith('-'):
+                if old or new:
+                    break
+                old = line
+            elif line.startswith('+'):
+                if not old or new:
+                    break
+                new = line
+        else:
+            if 'KEYWORDS=' in old and 'KEYWORDS=' in new:
+                return keyword_line_changes(old, new)
+        return None
+
+
+def apply_keyword_changes(ebuild: str, pathname: str,
+                          changes: List[Tuple[Optional[str],
+                                              Optional[str]]]) -> int:
+    result: int = 0
+
+    with tempfile.TemporaryDirectory() as tmpdir:
+        # ekeyword will only modify files named *.ebuild, so make a symlink
+        ebuild_symlink: str = os.path.join(tmpdir, os.path.basename(pathname))
+        os.symlink(os.path.join(os.getcwd(), ebuild), ebuild_symlink)
+
+        for removals, additions in changes:
+            args = []
+            for rem in removals:
+                # Drop leading '~' and '-' characters and prepend '^'
+                i = 1 if rem[0] in ('~', '-') else 0
+                args.append('^' + rem[i:])
+            if additions:
+                args.extend(additions)
+            args.append(ebuild_symlink)
+
+            result = ekeyword.main(args)
+            if result != 0:
+                break
+
+    return result
+
+
+def main(argv):
+    if len(argv) != 5:
+        sys.exit(-1)
+
+    O = argv[1] # %O - filename of original
+    A = argv[2] # %A - filename of our current version
+    B = argv[3] # %B - filename of the other branch's version
+    P = argv[4] # %P - original path of the file
+
+    # Get changes from %O to %B
+    changes = keyword_changes(O, B)
+    if changes:
+        # Apply O -> B changes to A
+        result: int = apply_keyword_changes(A, P, changes)
+        sys.exit(result)
+    else:
+        result: int = os.system(f"git merge-file -L HEAD -L base -L ours {A} {O} {B}")
+        sys.exit(0 if result == 0 else -1)
+
+
+if __name__ == "__main__":
+    main(sys.argv)