revset: replace _missingancestors optimization with only revset (::a - ::b) is equivalent to only(a, b).

tags: introduce _readtaghist function The existing _readtags function has been modified a little and renamed _readtaghist. A new _readtaghist function has been added, which is a wrappger around _readtaghist. Its output is the same as the old _readtaghist. The purpose of this change is to make it possible to automatically merge tag files. In order to do so we will need to get the line numbers for each of the tag-node pairs on the first merge parent. This is not used yet, but will be used on a follow up patch that will introduce an automatic tag merge algorithm. I performed some tests to compare the effect of this change. I used timeit to run the test-tags.t test a 9 times with and without this patch. The results were: - without this patch: 3 loops, best of 3: 8.55 sec per loop - with this patch: 3 loops, best of 3: 8.49 sec per loop The the test was on average was slightly faster with this patch (although the difference was probably not statistically significant).

subrepo: ensure "close()" execution at the end of "_initrepo()" Before this patch, "close()" for the file object opened in "_initrepo()" may not be executed, if unexpected exception is raised, because it isn't executed in "finally" clause. This patch ensures "close()" execution at the end of "_initrepo()" by moving it into "finally" clause. This patch puts configuration lines into "lines" array and write them out at once, to narrow the scope of "try"/"finally" for review-ability. This patch doesn't use "vfs.write()", because: - current "vfs.write()" implementation doesn't take "mode" argument to open file in "text" mode - writing hgrc file out in binary mode may break backward compatibility

subrepo: add test whether "[paths]" is configured correctly at subrepo creation This test is added for changes in the subsequent patch. This test doesn't use "(glob)" for expected output, because "[paths]" is configured at subrepo creation by "_abssource()" using "posixpath.join()" to join path components.

subrepo: ensure "close()" execution at the end of "_cachestorehash()" Before this patch, "close()" for the file object opened in "_cachestorehash()" may not be executed, if unexpected exception is raised, because it isn't executed in "finally" clause. This patch ensures "close()" execution at the end of "_cachestorehash()" by moving it into "finally" clause.

subrepo: ensure "close()" execution at the end of "_readstorehashcache()" Before this patch, "close()" for the file object opened in "_readstorehashcache()" may not be executed, if unexpected exception is raised, because it isn't executed in "finally" clause. This patch ensures "close()" execution at the end of "_readstorehashcache()" by moving it into "finally" clause.

subrepo: ensure "close()" execution at the end of "_calcfilehash()" Before this patch, "close()" for the file object opened in "_calcfilehash()" may not be executed, if unexpected exception is raised, because it isn't executed in "finally" clause. This patch ensures "close()" execution at the end of "_calcfilehash()" by moving it into "finally" clause.

subrepo: ensure "lock.release()" execution at the end of "_cachestorehash()" Before this patch, "lock.release()" for "self._repo" in "_cachestorehash()" of "hgsubrepo" may not be executed, if unexpected exception is raised, because it isn't executed in "finally" clause. This patch ensures "lock.release()" execution at the end of "_cachestorehash()" by moving it into "finally" clause.