Use characters from the beginning of the line up to the cursor column as the “fill prefix.” This prefix is prepended to each line in the paragraph. Cancel the prefix by typing this command in column 1.
Major mode: each tab defines a new indent for subsequent lines.
Exit indented text mode; return to text mode.
Indent a region to match first line in region.
Move cursor to first nonblank character on line.
Join this line to the previous one.
Split line at cursor; indent to column of cursor.
Reformat indented paragraphs, keeping indentation.