* "git mergetool" learned to take the "--[no-]gui" option, just like
"git difftool" does.
+ * "git rebase -i" learned a new insn, 'break', that the user can
+ insert in the to-do list. Upon hitting it, the command returns
+ control back to the user.
+
Performance, Internal Implementation, Development Support etc.
* Some tests have been reorganized and renamed; "ls t/" now gives a
better overview of what is tested for these scripts than before.
+ * "git rebase" and "git rebase -i" have been reimplemented in C.
+
Fixes since v2.19
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