simplemerge: avoid quadratic concatenation when building output text
I haven't checked if the difference is measurable, but the new version
is no less readable or idiomatic, so I don't think performance numbers
are needed.
Differential Revision: https://phab.mercurial-scm.org/D9549
# See http://EditorConfig.org for the specification
root = true
[*.py]
indent_size = 4
indent_style = space
trim_trailing_whitespace = true
end_of_line = lf
[*.{c,h}]
indent_size = 8
indent_style = tab
trim_trailing_whitespace = true
end_of_line = lf
[*.t]
indent_size = 2
indent_style = space
trim_trailing_whitespace = false
end_of_line = lf