revlog: avoid unnecessary node -> rev conversion

check-code: detect r.revision(r.node(rev)) revlog.revision takes either node or rev, but taking a rev is more efficient, because converting rev to node is just a seek and read. That's cheaper than converting node to rev, which may require O(n) walk in revlog index for the first times, and then triggering building the radix tree index. Even with the radix tree built, rev -> node is still faster than node -> rev because the radix tree requires more jumps in memory. So r.revision(r.node(rev)) should be changed to r.revision(rev). This patch adds a check-code rule to detect that.

hardlink: check directory's st_dev when copying files Previously, when copying a file, copyfiles will compare src's st_dev with dirname(dst)'s st_dev, to decide whether to enable hardlink or not. That could have issues on Linux's overlayfs, where stating directories could result in different st_dev from st_dev of stating files, even if both the directories and the files exist in the overlay's upperdir. This patch fixes it by checking dirname(src) instead. It's more consistent because we are checking directories for both src and dest. That fixes test-hardlinks.t running on common Docker setups.

hardlink: duplicate hardlink detection for copying files and directories A later patch will change one of them so they diverge.