Bug 74389

We are planning to write unit-tests for prepare-ChangeLog in a run-leaks_unittest manner. This bug is one of the incremental refactorings to remove all top-level code and global variables from prepare-ChangeLog. Global variables in prepare-ChangeLog can be categorized as follows: [A: Constant variables] $changeLogTimeZone $SVN $GIT %supportedTestExtensions [B: Arguments] $bugDescription $bugNumber $name $emailAddress $mergeBase $gitCommit $gitIndex $gitReviewer $openChangeLogs $writeChangeLogs $showHelp $spewDiff $updateChangeLogs $parseOptionsResult [C: Global variables that are used many times here and there] $isSVN $isGit [D: Global variables that are used only a few times] %paths $changedFiles $conflictFiles $functionLists $addedRegressionTests $bugURL $filesInChangeLog $prefixes $changeLogs In this bug, we remove all global variables in [D]. More accurately, we make all variables in [D] being used only through parameter passing.