Allow keywords as arguments to options and operands for the blame, diff, log, and tree commands. Also, return 1 when exiting tog with error rather than 0 so regress can discern success from failure. ok stsp@

This prevents mixing the use of got and cvg clients in the same work tree. Avoids confusion going forward while cvg differentiates itself further. tog(1) and gotadmin(1) remain compatible with both work tree formats. These tools only read work trees to locate the corresponding repository.

More work adding commit keyword support to the blame, cat, ref, tag, and tree commands. With this, all Got commands that take a <commit> option argument or operand now support keywords. Regress flub saved by op! fixes + ok op@

Add the ability to use keywords in the backout, branch, checkout, cherrypick, and patch commands. Includes some basic regress tests for the new commands, and also some more contrived test cases for 'got log -c[:]keyword[:(+|-)[N]]'. ok stsp

ok jamsek

This begins enabling the use of keywords in got wherever commit ids or references are used, with more work intended to expand support across all such instances (e.g., branch, checkout, etc.), and add more keywords. The keywords ":base" and ":head" can be passed to 'got {diff,log,update} -c' commands as a substitute for the corresponding commit hash id. Keywords and references can also be modified by appending a ':+' or ':-' and an optional integer N to specify by first parent traversal the Nth generation descendant or antecedent, respectively. If N is omitted, a '1' is implicitly appended. tweaks + ok op and stsp

ok jrick