suggested by stsp@; no functional change.

while here also wrap fcgi_send_response to make sure we don't end up trying to send a fcgi record bigger than allowed. ok tracey@

Rather than realloc in fixed-sized blocks, use the 1.5 * allocated scheme when growing the array. This produces fewer allocations and up to 3x speedup on large diffs. ok stsp@

Available to all views; for example, 99g will navigate to line 99 in the file if in a blame view or the 99th commit if in a log view. Includes improvements suggested by naddy and stsp. ok naddy@

ok tracey

ok op@

as originally intended by tracey@

fcgi_send_response can end up trying to send big amount of data, in particular when serving blobs. if a write failure occurs, gotwebd and httpd go out of sync and "bad stuff happens". debugged with and ok tracey@

there's no need to distinguish between plain text blob and a binary one in the output, just send it chunk by chunk. ok tracey@

ok tracey@

ok tracey@

suggested by stsp@

it's useful for e.g. to apply old patches that weren't generated by `got diff' or git-diff(1) and so lacks the metadata needed for the 3-way merge. manpage improvements from and ok stsp@

Current code is overly complex; it looks if the diff *might* use diff3 merge to postpone reverse_patch until we know for sure. Instead, just reverse_patch in apply_patch once we know if merge *is* used or not.