patch 8.1.1585: :let-heredoc does not trim enoughv8.1.1585

Problem:    :let-heredoc does not trim enough.
Solution:   Trim indent from the contents based on the indent of the first
            line.  Use let-heredoc in more tests.

1 files changed, 18 insertions, 7 deletions

diff --git a/runtime/doc/eval.txt b/runtime/doc/eval.txt
index 47ee2612b..1154c4065 100644
--- a/runtime/doc/eval.txt
+++ b/runtime/doc/eval.txt
@@ -11565,13 +11565,24 @@ text...
 			If {marker} is not supplied, then "." is used as the
 			default marker.
 
-			Any white space characters in the lines of text are
-			preserved.  If "trim" is specified before {marker},
-			then all the leading indentation exactly matching the
-			leading indentation before `let` is stripped from the
-			input lines and the line containing {marker}.  Note
-			that the difference between space and tab matters
-			here.
+			Without "trim" any white space characters in the lines
+			of text are preserved.  If "trim" is specified before
+			{marker}, then indentation is stripped so you can do: >
+				let text =<< trim END
+				   if ok
+				     echo 'done'
+				   endif
+				END
+<			Results in: ["if ok", "  echo 'done'", "endif"]
+			The marker must line up with "let" and the indentation
+			of the first line is removed from all the text lines.
+			Specifically: all the leading indentation exactly
+			matching the leading indentation of the first
+			non-empty text line is stripped from the input lines.
+			All leading indentation exactly matching the leading
+			indentation before `let` is stripped from the line
+			containing {marker}.  Note that the difference between
+			space and tab matters here.
 
 			If {var-name} didn't exist yet, it is created.
 			Cannot be followed by another command, but can be