Fix StackOverflowError during cherry-pick submit

Using a regex pattern of "^(\n|.)*\n..." causes the Java regex package
to recurse for each consideration of the first alternation, creating a
very deep stack for a relatively short commit message.  If the message
is large enough, the thread stack overflows, and an exception is thrown.

Instead we use a more customized parser, to examine the message end and
determine if an LF should be appended, or not.

Bug: GERRIT-207
Signed-off-by: Shawn O. Pearce <sop@google.com>

1 files changed, 29 insertions, 7 deletions

diff --git a/src/main/java/com/google/gerrit/git/MergeOp.java b/src/main/java/com/google/gerrit/git/MergeOp.java
index 5dcd27d7da..0f09e6d069 100644
--- a/src/main/java/com/google/gerrit/git/MergeOp.java
+++ b/src/main/java/com/google/gerrit/git/MergeOp.java
@@ -502,7 +502,7 @@ public class MergeOp {
       // Missing a trailing LF? Correct it (perhaps the editor was broken).
       msgbuf.append('\n');
     }
-    if (!msgbuf.toString().matches("^(\n|.)*\n[A-Za-z0-9-]{1,}: [^\n]{1,}\n$")) {
+    if (!endsWithKey(msgbuf.toString())) {
       // Doesn't end in a "Signed-off-by: ..." style line? Add another line
       // break to start a new paragraph for the reviewed-by tag lines.
       //
@@ -623,6 +623,24 @@ public class MergeOp {
     newCommits.put(n.patchsetId.getParentKey(), mergeTip);
   }
 
+  private boolean endsWithKey(final String msg) {
+    if (msg.length() == 0 || !msg.endsWith("\n") || msg.length() < 2) {
+      return false;
+    }
+
+    final int lf = msg.lastIndexOf('\n', msg.length() - 2);
+    if (lf == -1) {
+      return false;
+    }
+
+    final String line = msg.substring(lf + 1);
+    final int c = line.indexOf(':');
+    if (c == -1) {
+      return false;
+    }
+    return line.substring(0, c).matches("[A-Za-z][A-Za-z0-9-]*[A-Za-z0-9]");
+  }
+
   private void updateBranch() throws MergeException {
     if (branchTip == null || branchTip != mergeTip) {
       branchUpdate.setForceUpdate(false);
@@ -712,14 +730,16 @@ public class MergeOp {
             final MergeFailSender cm = new MergeFailSender(server, c);
             cm.setFrom(getSubmitter(c));
             cm.setReviewDb(schema);
-            cm.setPatchSet(schema.patchSets().get(c.currentPatchSetId()), schema
-                .patchSetInfo().get(c.currentPatchSetId()));
+            cm.setPatchSet(schema.patchSets().get(c.currentPatchSetId()),
+                schema.patchSetInfo().get(c.currentPatchSetId()));
             cm.setChangeMessage(msg);
             cm.send();
           } catch (OrmException e) {
-            log.error("Cannot submit patch set for Change " + c.getId() + " due to a missing dependency.", e);
+            log.error("Cannot submit patch set for Change " + c.getId()
+                + " due to a missing dependency.", e);
           } catch (EmailException e) {
-            log.error("Cannot submit patch set for Change " + c.getId() + " due to a missing dependency.", e);
+            log.error("Cannot submit patch set for Change " + c.getId()
+                + " due to a missing dependency.", e);
           }
 
           break;
@@ -871,9 +891,11 @@ public class MergeOp {
       cm.setChangeMessage(msg);
       cm.send();
     } catch (OrmException e) {
-      log.error("Cannot submit patch set for Change " + c.getId() + " due to a path conflict.", e);
+      log.error("Cannot submit patch set for Change " + c.getId()
+          + " due to a path conflict.", e);
     } catch (EmailException e) {
-      log.error("Cannot submit patch set for Change " + c.getId() + " due to a path conflict.", e);
+      log.error("Cannot submit patch set for Change " + c.getId()
+          + " due to a path conflict.", e);
     }
   }
 }