revset: introduce "_parsealiasdecl" to parse alias declarations strictly This patch introduces "_parsealiasdecl" to parse alias declarations strictly. For example, "_parsealiasdecl" can detect problems below, which current implementation can't. - un-closed parenthesis causes being treated as "alias symbol" because all of declarations not in "func(....)" style are recognized as "alias symbol". for example, "foo($1, $2" is treated as the alias symbol. - alias symbol/function names aren't examined whether they are valid as symbol or not for example, "foo bar" can be treated as the alias symbol, but of course such invalid symbol can't be referred in revset. - just splitting argument list by "," causes overlooking syntax problems in the declaration for example, all of invalid declarations below are overlooked: - foo("bar") => taking one argument named as '"bar"' - foo("unclosed) => taking one argument named as '"unclosed' - foo(bar::baz) => taking one argument named as 'bar::baz' - foo(bar($1)) => taking one argument named as 'bar($1)' To decrease complication of patch, current implementation for alias declarations is replaced by "_parsealiasdecl" in the subsequent patch. This patch just introduces it. This patch defines "_parsealiasdecl" not as a method of "revsetalias" class but as a one of "revset" module, because of ease of testing by doctest. This patch factors some helper functions for "tree" out, because: - direct accessing like "if tree[0] == 'func' and len(tree) > 1" decreases readability - subsequent patch (and also existing code paths, in the future) can use them for readability This patch also factors "_tokenizealias" out, because it can be used also for parsing alias definitions strictly.

revset: store full detail into revsetalias.error for error source distinction Before this patch, any errors in the declaration of revset alias aren't detected at all, and there is no information about error source in the error message. As a part of preparation for parsing alias declarations and definitions more strictly, this patch stores full detail into "revsetalias.error" for error source distinction. This makes raising "Abort" and warning potential errors just use "revsetalias.error" without any message composing.

revset: factor out composing error message for ParseError to reuse This patch defines the composing function not in "ParseError" class but in "revset" module, because: - "_()" shouldn't be used in "ParseError", to avoid adding "from i18n import _" i18n" to "error" module - generalizing message composition of"ParseError" for all code paths other than revset isn't the purpose of this patch we should also take care of showing "unexpected leading whitespace" for some code paths, to generalize widely.

revset: make tokenize extensible to parse alias declarations and definitions Before this patch, "tokenize" doesn't recognize the symbol starting with "$" as a valid one. This prevents revset alias declarations and definitions from being parsed with "tokenize", because "$" may be used as the initial letter of alias arguments. BTW, the alias argument name doesn't require leading "$" itself, in fact. But we have to assume that users may use "$" as the initial letter of argument names in their aliases, because examples in "hg help revsets" uses such names for a long time. To make "tokenize" extensible to parse alias declarations and definitions, this patch introduces optional arguments "syminitletters" and "symletters". Giving these sets can change the policy of "valid symbol" in tokenization easily. This patch keeps original examination of letter validity for reviewability, even though there is redundant interchanging between "chr"/"ord" at initialization of "_syminitletters" and "_symletters". At most 256 times examination (per initialization) is cheaper enough than revset evaluation itself. This patch is a part of preparation for parsing alias declarations and definitions more strictly.