Commit Briefs
put functions required for using diff_output_unidiff_chunk() into public API
They will be needed to implement 'got stage -p' and 'got revert -p', etc. Chunks stored in diff_result still need post-processing in order to be displayed as expected by diff_output_unidiff_chunk(). Exposing these functions allows API consumers to implement the same chunk merging loop as used internally by output_unidiff() and output_edscript(). (Perhaps, ideally, the public diff API would provide pre-merged chunks at some point in the future? Then this commit could probably be reverted.) Change return values from bool to int to avoid making stdbool.h a requirement for the public diff API.
use mergesort(3) instead of qsort(3) in patience diff
Fixes test failures on OpenBSD due to unstable results of qsort if two or more elements are equal. Add a compat copy of OpenBSD mergesort(3) for Linux.
print "\ No newline at end of file" message like UNIX diff(1) does
Not adding new tests since this behaviour is covered by tests in Got.
add test for -T option
This uncovered a bug in diff_algo_none(), so let's keep it.
move patience data out of struct diff_atom
Now allocating patience specific data only when patience is going to be used. This may allow using forward-Myers more often, since the state size per line is significantly smaller. Patience instead allocates an array, puts it in the current diff_data, and also place a pointer of the current diff_data in the root diff_data (since each atom points to the root diff_data).
rename diff_atom->d to diff_atom->root, because it always is
The idea was that for each diff box within the files, the atoms would have a backpointer to the current layer of diff_data (indicating the current section), but it is not actually needed to update the backpointer in each atom to the current diff_data. That is why the current code always points atom->d to the root diff_data for the entire file. Clarify by proper name. Constructs like atom->d->root->foo are redundant, just use atom->root->foo.
diff: drop -p, add -P -Q -T; diffreg(): use algo enum
-p is traditionally used for "show which C function each change is in", so don't use it for choosing Patience. Instead add two options for using Patience, -P for only Patience and -Q to attempt forward-Myers first. Also add -T for a trivial diff (diff_algo_none).