s/StringBuffer/StringBuilder as appropriate where no concurrency is needed

org.eclipse.jgit/src/org/eclipse/jgit/lib/Config.java

org.eclipse.jgit/src/org/eclipse/jgit/lib/FileTreeEntry.java

...lipse.jgit/src/org/eclipse/jgit/lib/GitlinkTreeEntry.java

org.eclipse.jgit/src/org/eclipse/jgit/lib/PersonIdent.java

...lipse.jgit/src/org/eclipse/jgit/lib/SymlinkTreeEntry.java

org.eclipse.jgit/src/org/eclipse/jgit/lib/Tag.java

org.eclipse.jgit/src/org/eclipse/jgit/lib/Tree.java

org.eclipse.jgit/src/org/eclipse/jgit/lib/TreeEntry.java

...git/src/org/eclipse/jgit/revwalk/filter/AndRevFilter.java

...jgit/src/org/eclipse/jgit/revwalk/filter/OrRevFilter.java

...t/src/org/eclipse/jgit/treewalk/filter/AndTreeFilter.java

...it/src/org/eclipse/jgit/treewalk/filter/OrTreeFilter.java

...src/org/eclipse/jgit/treewalk/filter/PathFilterGroup.java