fix: gate single-word displayName matches on metadata and block placeholder names (CM-1137)

Signed-off-by: Yeganathan S <63534555+skwowet@users.noreply.github.com>

Author: skwowet

services/apps/merge_suggestions_worker/src/memberSimilarityCalculator.ts

@@ -178,7 +178,18 @@ class MemberSimilarityCalculator {
     if (
       similarMember.keyword_displayName.toLowerCase() === primaryMember.displayName.toLowerCase()
     ) {
-      return this.decideMemberSimilarityUsingAdditionalChecks(primaryMember, similarMember)
+      const dn = primaryMember.displayName.toLowerCase().trim()
+      if (isOsReservedName(dn)) {
+        return this.LOW_CONFIDENCE_SCORE
+      }
+      // Single-word names (first-name-only, handles) are too ambiguous without a corroborating
+      // signal. Multi-word names (full names) are treated as high-confidence on their own.
+      const isFullName = dn.includes(' ')
+      return this.decideMemberSimilarityUsingAdditionalChecks(
+        primaryMember,
+        similarMember,
+        isFullName ? undefined : this.HIGH_CONFIDENCE_SCORE,
+      )
     }
 
     // calculate similarity percentage

services/apps/merge_suggestions_worker/src/utils.ts

@@ -52,7 +52,16 @@ export function stripProtocol(value: string) {
 
 // Generic git user.name placeholders and OS account names that are never a real human
 // identity — shared across unrelated machines and meaningless as a merge signal.
-const OS_RESERVED_NAMES = new Set(['unknown', 'root', 'ubuntu', 'admin', 'user', 'guest'])
+const OS_RESERVED_NAMES = new Set([
+  'unknown',
+  'root',
+  'ubuntu',
+  'admin',
+  'user',
+  'guest',
+  '[[unknown]] [not provided]',
+  'deleted user',
+])
 
 export function isOsReservedName(name: string): boolean {
   return OS_RESERVED_NAMES.has(name.trim().toLowerCase())