Abort on conflicting ref names

If you have a ref name refs/tags/foo you cannot create a ref refs/tags/foo/bar
and also the other way around, as for the former a file and the the latter a directory
would be created that both would be named 'foo' as long as the refs are not packed.

So check for this and abort early so that the rules can be adapted to produce proper names.

Author: Vampire

src/repository.cpp

@@ -53,7 +53,7 @@ class FastImportRepository : public Repository
         inline Transaction() {}
     public:
         ~Transaction();
-        void commit();
+        int commit();
 
         void setAuthor(const QByteArray &author);
         void setDateTime(uint dt);
@@ -162,7 +162,7 @@ class ForwardingRepository : public Repository
     public:
         Transaction(Repository::Transaction *t, const QString &p) : txn(t), prefix(p) {}
         ~Transaction() { delete txn; }
-        void commit() { txn->commit(); }
+        int commit() { return txn->commit(); }
 
         void setAuthor(const QByteArray &author) { txn->setAuthor(author); }
         void setDateTime(uint dt) { txn->setDateTime(dt); }
@@ -978,12 +978,21 @@ void FastImportRepository::Transaction::commitNote(const QByteArray &noteText, b
     }
 }
 
-void FastImportRepository::Transaction::commit()
+int FastImportRepository::Transaction::commit()
 {
+    foreach (QString branchName, repository->branches.keys())
+    {
+        if (branchName.toUtf8().startsWith(branch + "/") || branch.startsWith((branchName + "/").toUtf8()))
+        {
+            qCritical() << "Branch" << branch << "conflicts with already existing branch" << branchName;
+            return EXIT_FAILURE;
+        }
+    }
+
     repository->startFastImport();
 
     // We might be tempted to use the SVN revision number as the fast-import commit mark.
-    // However, a single SVN revision can modify multple branches, and thus lead to multiple
+    // However, a single SVN revision can modify multiple branches, and thus lead to multiple
     // commits in the same repo.  So, we need to maintain a separate commit mark counter.
     mark_t  mark = ++repository->last_commit_mark;
 
@@ -1082,4 +1091,6 @@ void FastImportRepository::Transaction::commit()
     while (repository->fastImport.bytesToWrite())
         if (!repository->fastImport.waitForBytesWritten(-1))
             qFatal("Failed to write to process: %s for repository %s", qPrintable(repository->fastImport.errorString()), qPrintable(repository->name));
+
+    return EXIT_SUCCESS;
 }

src/repository.h

@@ -101,7 +101,7 @@ class Repository
         Transaction() {}
     public:
         virtual ~Transaction() {}
-        virtual void commit() = 0;
+        virtual int commit() = 0;
 
         virtual void setAuthor(const QByteArray &author) = 0;
         virtual void setDateTime(uint dt) = 0;

src/svn.cpp

@@ -602,7 +602,8 @@ int SvnRevision::commit()
         txn->setDateTime(epoch);
         txn->setLog(log);
 
-        txn->commit();
+        if (txn->commit() != EXIT_SUCCESS)
+            return EXIT_FAILURE;
         delete txn;
     }