* ResolveMerger: do not content-merge gitlinks on del/mod conflicts
* ResolveMerger: Adding test cases for GITLINK deletion
* ResolveMerger: choose OURS on gitlink when ignoreConflicts
* ResolveMerger: improving content merge readability
* ResolveMerger: extracting createGitLinksMergeResult method
* ResolveMerger: Adding test cases for GITLINK merge
* UploadPack: Create a method that propagates an exception as-is
* UploadPack: Consolidate the sideband handling code to one place
* UploadPack: Introduce ErrorWriter