doc: describe -L pickaxe scoping for -S and -G

This series documents the -L stat formats as range-scoped and scopes
-G to the tracked range, but -S still matches the whole file.  Spell
out the distinction so -S's whole-file behavior is not mistaken for the
range-scoped behavior of -G and the formats listed alongside it.

Signed-off-by: Michael Montalbo <mmontalbo@gmail.com>

Author: mmontalbo

Documentation/line-range-options.adoc

@@ -20,6 +20,9 @@
 +
 Patch formatting options such as `--word-diff`, `--color-moved`,
 `--no-prefix`, and whitespace options (`-w`, `-b`) are supported,
-as are pickaxe options (`-S`, `-G`) and `--diff-filter`.
+as are pickaxe options (`-S`, `-G`) and `--diff-filter`.  `-G` is
+scoped to the tracked range; `-S` is still evaluated over the whole
+file, so an `-S` query may select a commit for a change outside the
+range.
 +
 include::line-range-format.adoc[]