# HG changeset patch
# User Artem Tikhomirov <tikhomirov.artem@gmail.com>
# Date 1303955085 -7200
# Node ID 9ce3b26798c4320b8585988437ff798773f8cd0a
# Parent  ef8eba4aa2157b33e179fe9f52d5373251d9faf3
Few branches (distinct BranchChains from distinct heads) may end up with same nodes. Building BC structure fixed to reuse chain elements

diff -r ef8eba4aa215 -r 9ce3b26798c4 design.txt
--- a/design.txt	Thu Apr 28 03:17:50 2011 +0200
+++ b/design.txt	Thu Apr 28 03:44:45 2011 +0200
@@ -67,6 +67,9 @@
 
 -cancellation and progress support
 -timestamp check for revlog to recognize external changes
+-HgDate or any other better access to time info
+-(low) RepositoryComparator#calculateMissingBranches may query branches for the same head more than once 
+	(when there are few heads that end up with common nodes). e.g hg4j revision 7 against remote hg4j revision 206 
 
 >>>> Effective file read/data access
 ReadOperation, Revlog does: repo.getFileSystem().run(this.file, new ReadOperation(), long start=0, long end = -1)
diff -r ef8eba4aa215 -r 9ce3b26798c4 src/org/tmatesoft/hg/internal/RepositoryComparator.java
--- a/src/org/tmatesoft/hg/internal/RepositoryComparator.java	Thu Apr 28 03:17:50 2011 +0200
+++ b/src/org/tmatesoft/hg/internal/RepositoryComparator.java	Thu Apr 28 03:44:45 2011 +0200
@@ -249,11 +249,26 @@
 					boolean hasP1 = !NULL.equals(rb.p1), hasP2 = !NULL.equals(rb.p2);  
 					if (hasP1 && !localRepo.knownNode(rb.p1)) {
 						toQuery.add(rb.p1);
-						head2chain.put(rb.p1, chainElement.p1 = new BranchChain(rb.p1));
+						// we might have seen parent node already, and recorded it as a branch chain
+						// we shall reuse existing BC to get it completely initializer (head2chain map
+						// on second put with the same key would leave first BC uninitialized.
+						
+						// It seems there's no reason to be affraid (XXX although shall double-check)
+						// that BC's chain would get corrupt (its p1 and p2 fields assigned twice with different values)
+						// as parents are always the same (and likely, BC that is common would be the last unknown)
+						BranchChain bc = head2chain.get(rb.p1);
+						if (bc == null) {
+							head2chain.put(rb.p1, bc = new BranchChain(rb.p1));
+						}
+						chainElement.p2 = bc;
 					}
 					if (hasP2 && !localRepo.knownNode(rb.p2)) {
 						toQuery.add(rb.p2);
-						head2chain.put(rb.p2, chainElement.p2 = new BranchChain(rb.p2));
+						BranchChain bc = head2chain.get(rb.p2);
+						if (bc == null) {
+							head2chain.put(rb.p2, bc = new BranchChain(rb.p2));
+						}
+						chainElement.p2 = bc;
 					}
 					if (!hasP1 && !hasP2) {
 						// special case, when we do incoming against blank repository, chainElement.branchRoot