filemerge: add 'union' merge to internal merge tool 'union merge' is a merge strategy which adds both left and right hand side of a conflict region. Git implements this merge strategy which is very practical to have for merging e.g. the Changelog file.

filemerge: split internal merge into api entry point and internal helper This is a step toward adding 'union merge' to the internal merge tool. 'union merge' is a merge strategy which adds both left and right hand side of a conflict region. Git implements this merge strategy which is very practical to have for merging to e.g. the Changelog file.

simplemerge: add 'mode' kwarg which - when 'union' - suppresses markers This is a step toward adding 'union merge' to the internal merge tool. 'union merge' is a merge strategy which adds both left and right hand side of a conflict region. Git implements this merge strategy which is very practical to have for merging to e.g. the Changelog file. Note: the identifiers with underscores in this commit are all using existing variable names and/or keyword arguments.

hghave: remove quiet option The --quiet flag appears to be unused. Kill it.

hghave: move feature checking into hghave.py Upcoming patches will kill hghave (the script - not hghave.py) and will move to a model where requirements checking is performed as a function call. Start diminishing the utility of hghave by moving some code to hghave.py.

tests: move '#require bzr' into .t files The bzr tests are the only .t tests calling hghave (aside from the tests testing hghave itself). This pattern is a one-off and prevents desired refactors to how requirements checking is integrated into tests. Use the convention used everywhere else.