templater: teach template loader to use open_template() function The template loader can apparently load templates from relative paths, so I needed to add that support to `open_template()`. This takes the number of failing tests with PyOxidizer from 54 to 34. Differential Revision: https://phab.mercurial-scm.org/D8907

templater: restructure open_template() a little to prepare for relative paths I found that it was easier to add support for relative paths after this restructuring. It also made it easier to explain each case with a code comment (which I did). Differential Revision: https://phab.mercurial-scm.org/D8906

templater: add exception-raising version of open_template() I'm about to add another caller of `open_template()` (in the template loader). That caller will want to get exceptions instead of `(None, None)` if the template doesn't exist. This patch therefore changes `open_template()` to raise exceptions and adds a new `try_open_template()` that returns the `(None, None)` value. Differential Revision: https://phab.mercurial-scm.org/D8905

templater: replace Py3-only exception types by super-types available in Py2 As noted by @indygreg, `test-check-pyflakes.t` started failing on Py2 after my recent D8894, because that introduced catching of the Py3-only types `ModuleNotFoundError` and `FileNotFoundError`. Let's switch to less precise types that are also available in Py2. Differential Revision: https://phab.mercurial-scm.org/D8902

hgweb: enable reading styles from resources in frozen binaries All we need to do to read styles from resources is to pass the file-like object we get from `open_template()` on to `frommapfile()`. This takes the number of failing tests with PyOxidizer from 62 to 54. Differential Revision: https://phab.mercurial-scm.org/D8901

hgweb: rely on open_template()'s fallback to using templatedir() Differential Revision: https://phab.mercurial-scm.org/D8900

hgweb: open mapfile using templater.open_template() This will help us read templates from resources in frozen binaries. Differential Revision: https://phab.mercurial-scm.org/D8899

hgweb: simplify a constant-length list by converting to literal tuple The call to `.append()` has been unnecessary since d3dbdca92458 (hgweb: don't choke when an inexistent style is requested (issue1901), 2009-11-12). Differential Revision: https://phab.mercurial-scm.org/D8898

hgweb: remove some accesses to private member uimod._unset Differential Revision: https://phab.mercurial-scm.org/D8897

templater: try to read %include in mapfiles from resources The "show" style is an example of a style that uses an "%include" statement in its definition. This patch makes `hg log --style show` work. This takes the number of failing tests with PyOxidizer from 72 to 62. Differential Revision: https://phab.mercurial-scm.org/D8896

templater: unroll loop over mapfile directories I'll rewrite the handling of the `templatedir()` case in the next patch, so the two cases will be more different and the loop won't make as much sense. Differential Revision: https://phab.mercurial-scm.org/D8895

templater: make open_template() read from resources if in frozen binary This takes the number of failing tests with PyOxidizer from 87 to 72. Differential Revision: https://phab.mercurial-scm.org/D8894

templater: pass opened file-like object to templatespec I think I said earlier that I planned to create a special templatespec variant for built-in templates. That was true (I planned that), but I ended up (in this patch) just adding a file-like object to the `mapfile_templatespec()` variant instead. Differential Revision: https://phab.mercurial-scm.org/D8893

templater: replace templatepath() with function that also opens the file For frozen binaries, such as those created by PyOxidizer, I plan to make it so the templatespec can keep an opened file/resource to read from instead of needing a file path. Having `templatepath()` return an opened file should help with that. At this point, it's just a wasteful extra opening of mapfiles that we'll open again later. I'll update the read-side next so it reads from the file-like object without opening the file again. Differential Revision: https://phab.mercurial-scm.org/D8892

templater: start passing resource to read from into _readmapfile() This patch makes it so we pass in a file-like resource to read from instead of having `_readmapfile()` open the file. This is one more step towards making `_readmapfile()` able to read resources opened by from `importlib.resources`. We still need to pass in the mapfile path because it's used for loading dependent mapfiles from `%include` and `__base__`, and it's also used for giving the user better error messages. Besides that, one can safely call `_readmapfile()` with any file-like resource after this patch. Differential Revision: https://phab.mercurial-scm.org/D8891

templater: move stylemap() to hgweb_mod, since that's its only user `stylemap()` even has an error message that mentions "hgweb templates", so it seems that it's meant specifically for hgweb. Differential Revision: https://phab.mercurial-scm.org/D8890