Documented the ledger line changes.

Part of the implementation for gregorio-project#1215.

CHANGELOG.md

@@ -9,7 +9,8 @@ As of v3.0.0 this project adheres to [Semantic Versioning](http://semver.org/).
 
 ## Changed
 - Notes are now left-aligned as if all clefs had the same width as the largest clef in the score. You can get previous behavior back with `\grebolshiftcleftype{current}`, or temporary force alignment until the end of a score with `\grelocalbolshiftcleftype`. See Documentation of these functions and [#1189](https://github.com/gregorio-project/gregorio/issues/1189).
-- A clef change immediately before a line break `(z)` will now typeset the new clef at the beginning of the next line.  An explicit custos `(z0)` immediately before such a clef change (or separated by only a bar) will be suppressed.  See [1190](https://github.com/gregorio-project/gregorio/issues/1190).
+- A clef change immediately before a line break `(z)` will now typeset the new clef at the beginning of the next line.  An explicit custos `(z0)` immediately before such a clef change (or separated by only a bar) will be suppressed.  See [#1190](https://github.com/gregorio-project/gregorio/issues/1190).
+- Ledger lines are now extended by default through higher pitched notes on either side of a ledger line.  If the algorithm doesn't produce the result you want, you can use `[oll:0]` to suppress an over-the-staff ledger line on a note, `[ull:0]` to suppress an under-the-staff ledger line on a note, `[oll:1]` to force an over-the-line ledger line on a note, or [ull:1] to force an under-the-staff ledger line on a note.  Please note that other forms of `[oll:...]` and `[ull:...]` can interfere with these new settings. See [UPGRADE.md](UPGRADE.md) and [#1215](https://github.com/gregorio-project/gregorio/issues/1215) for details.
 
 ### Added
 - More cavum shapes are now available.  To use them, simply add `r` in gabc to any note in a glyph.  See [#844](https://github.com/gregorio-project/gregorio/issues/844).

UPGRADE.md

@@ -2,14 +2,27 @@
 
 This file contains instructions to upgrade to a new release of Gregorio.
 
-## Next version
+## 5.0
 
 ### Gregorio and Grana Padano fonts
 
 The gregorio and granapadano fonts, as well as their "-op" Dominican variants, will now be available as separate downloads.  If you were using these fonts, either download and install them or switch to greciliae, which continues to be distributed along with Gregorio by default.
 
 *** NOTE: put the logistics of these downloads here once they've been determined ***
 
+### Ledger lines
+
+As of version 5.0, ledger lines are extended through higher pitched notes on either side of a ledger line.
+
+The algorithm for this is simple so it can be predictable, but this means it may not produce the exactly desired results.  In order to get the results you want, you can override the automatic behavior in gabc:
+
+- `[oll:1]` will force an over-the-staff ledger line on a note.
+- `[oll:0]` will suppress an over-the-staff ledger line on a note.
+- `[ull:1]` will force an under-the-staff ledger line on a note.
+- `[ull:0]` will suppress an under-the-staff ledger line on a note.
+
+The other `oll` and `ull` forms take precendence over and will interfere with the above settings, so if you are using them, you may need to adjust them to get the output you want.
+
 ## 4.2
 
 ### Executable file name