doc: add a section about visual selection (fix #33)

README.md

@@ -97,6 +97,18 @@ There are 5 sections:
   * only lines starting with a + sign can be modified
   * no line can be deleted
 
+### Visual selection
+
+It is possible to stage part of hunk, by different ways:
+* By visually selecting some lines, then staging the selection with **S**.
+* By marking some lines "to be staged" with **M**, then staging these selected lines with **S**.
+* Staging individual lines with **L**.
+
+Visual selection and marked lines have some limitations for the moment:
+* It only work for "staging", not for "unstaging".
+* Selection/marks must be within a single hunk.
+* Marks not within the hunk currently staged are lost during stage process magit buffer refresh.
+
 ### Commands
 
 #### magit#show_magit()

doc/vimagit.txt

@@ -109,6 +109,19 @@ INLINE MODIFICATIONS                               *vimagit-inline-modification*
   * only lines starting with a + sign can be modified
   * no line can be deleted
 
+VISUAL SELECTION                                      *vimagit-visual-selection*
+
+It is possible to stage part of hunk, by different ways:
+* By visually selecting some lines, then staging the selection with S.
+* By marking some lines "to be staged" with M, then staging these selected
+  lines with S.
+* Staging individual lines with L.
+
+Visual selection and marked lines have some limitations for the moment:
+* It only work for "staging", not for "unstaging".
+* Selection/marks must be within a single hunk.
+* Marks not within the hunk currently staged are lost during stage process magit
+  buffer refresh.
 
 COMMANDS                                                      *vimagit-commands*