revset: use try-except instead of if-else because of perf For wdir(), we now raises an exception which will be raised when wdir() will be passed, so catching that exception is better checking for wdir() using if-else.

revset: remove redundant condition and change to else from elif Before going to this piece of code, we already check whether n is in [0, 1, 2], so dropping the redundant condition.

tests: add tests for predicates and operators which works with wdir() This one is cluttering up the test file though.

revset: add support for "wdir()^n" This patch catches the WdirUnsupported exception raised, and adds support for wdir^n which will give us the nth parent of the working directory.

revset: add parentheses after wdir since its a function wdir was shown in help rather than wdir().

cmdutil: avoid redefining write() function in export if possible Doing less work inside the loop just feels better to me.

cmdutil: extract closure that performs the actual export formatting This simplifies things a little by making the actual act of turning a revision into patch data a single function. After this, adding formatter support to `hg export` should be much simpler.