This guards against {mis,ab}use such as `tog < /dev/null`. ok plus fix from op@

We fail to release the memory for the nodes. To fix it however, we some consumer of the commit graph iterator need to be corrected: the returned pointer is safe to be used only up until the next iter_next call; save a copy it if it's needed afterwards too. ok stsp@

ok stsp@

patch by Josiah Frentsos

ok jamsek

As per stsp's TODO item, make tog respond to key presses while "loading..." history. Initial testing in src.git appears to work as intended. ok stsp@

If a child blame view has been opened, halfdelay() is reset to a 1 second refresh rate, so the index in the header lags behind subtree navigation as we set the index based on the selected tree entry, which isn't updated till that refresh cycle completes. Don't wait for the selected_entry to update; instead, compute the index from the first displayed entry and the currently selected line index. improved by and ok stsp@

Previously, we only handled 'G' in log_move_cursor_down() when all commits had not yet been loaded; move the case where all commits are already loaded into this routine too, and simplify by handling both cases the same. This change was prompted by Mikhail's observation of a redundant assignment in the previous 'G' handling in log_move_cursor_down(). ok stsp@

When at the end of the log view such that the currently selected line is greater than nlines/2, add--don't assign--the page down value to the selected index so we don't jump up when the user expects tog to scroll down. While here, rework log page down logic for a smoother UX in horizontal split mode by moving the selection cursor down rather than scrolling when 'd' or 'f' is entered if the last commit is already on screen. ok stsp@

ok stsp@

Add () and {} key maps to navigate to the previous and next file or hunk in the diff. This required changing Got's diff API to collect line type metadata in addition to the line offsets already produced as prompted by stsp. 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@

Deduplicate view initialisation boilerplate and simplify new key map view requests with dispatch routine. Includes improvements suggested by stsp. ok stsp@