Add edit mode and related help

An example to show to how to use this feature has been added.

ref #152

README.md

@@ -122,9 +122,52 @@ There are 5 sections:
 * Stash list: this section contains all stahes.
 
 ### Inline modifications
-* It is possible to modify the content to be staged or unstaged in magit buffer, with some limitations:
+* It is possible to modify the content of a hunk to be staged or unstaged, with some limitations:
   * only lines starting with a + sign can be modified
-  * no line can be deleted
+  * no lines can be deleted
+
+Let's imagine we have the following hunk:
+```diff
+-int main() {
+-       printf("Hello world\n");
+-       return 0;
++int main(int argc, const char *argv[]) {
++       int ret = printf("Hello world: %s\n", argv[0]);
++       return (ret > 0);
+```
+Ideally, we would like two commits here: one adding the argv parameter, and one checking the printf return value.
+
+One way to do so is to edit the file, deleting the return value code, stage, commit the argv feature; then, go back to source file, undo previous deletion, stage, and commit the return value feature.
+
+Another way is to edit the hunk from the magit buffer!
+
+Enter in edition mode with the mapping <kbd>E</kbd>, and start to edit the
+hunk, to remove the return value feature. After edition, you should have this
+result:
+```diff
+-int main() {
+-	printf("Hello world\n");
+-	return 0;
++int main(int argc, const char *argv[]) {
++	printf("Hello world: %s\n", argv[0]);
++	return 0;
+```
+Stage the hunk, as is. Now you can see that you have the argv feature in staged section:
+```diff
+-int main() {
+-	printf("Hello world\n");
++int main(int argc, const char *argv[]) {
++	printf("Hello world: %s\n", argv[0]);
+```
+And that you have the return value feature in unstaged section:
+```diff
+-	printf("Hello world: %s\n", argv[0]);
+-	return 0;
++	int ret = printf("Hello world: %s\n", argv[0]);
++	return (ret > 0);
+```
+
+Voilà, you just did your first partial line staging!
 
 ### Visual selection
 
@@ -291,6 +334,13 @@ Some mappings are set for the whole magit buffer, others are set for specific se
 
  * Add the file under the cursor in .gitgnore
 
+<kbd>E</kbd>
+
+* Set the magit buffer in edit mode, allowing to edit a hunk before staging it.
+* Edit mode is left after stage/unstage command, or a refresh command.
+
+See [inline modifications](inline_modifications)  to learn how to use this feature.
+
 -----------------------------------
 
 <kbd>J</kbd>, <kbd>Ctrl</kbd>+<kbd>]</kbd>

autoload/magit/mapping.vim

@@ -8,6 +8,7 @@ let g:magit_commit_amend_mapping   = get(g:, 'magit_commit_amend_mapping',
 let g:magit_commit_fixup_mapping   = get(g:, 'magit_commit_fixup_mapping',      'CF' )
 let g:magit_close_commit_mapping   = get(g:, 'magit_close_commit_mapping',      'CU' )
 let g:magit_reload_mapping         = get(g:, 'magit_reload_mapping',            'R' )
+let g:magit_edit_hunk_mapping      = get(g:, 'magit_edit_hunk_mapping',         'E' )
 let g:magit_edit_mapping           = get(g:, 'magit_edit_mapping',              'J' )
 
 let g:magit_jump_next_hunk         = get(g:, 'magit_jump_next_hunk',            '<C-N>')
@@ -127,6 +128,9 @@ function! magit#mapping#set_default()
 
 	call s:mg_set_mapping('n', g:magit_ignore_mapping,
 				\ "magit#ignore_file()", '\<\%(un\)\?staged\>')
+	call s:mg_set_mapping('n', g:magit_edit_hunk_mapping,
+				\ "magit#edit_hunk()", '\<\%(un\)\?staged\>')
+
 	call s:mg_set_mapping('n', g:magit_edit_mapping,
 				\ "magit#jump_to()", '\<\%(un\)\?staged\>')
 	call s:mg_set_mapping('n', '<C-]>',

doc/vimagit.txt

@@ -117,10 +117,56 @@ There are 5 sections:
 
 INLINE MODIFICATIONS                               *vimagit-inline-modification*
 
-* It is possible to modify the content to be staged or unstaged in magit
-  buffer, with some limitations:
+* It is possible to modify the content of a hunk to be staged or unstaged,
+  with some limitations:
   * only lines starting with a + sign can be modified
-  * no line can be deleted
+  * no lines can be deleted
+
+Let's imagine we have the following hunk: >
+ -int main() {
+ -       printf("Hello world\n");
+ -       return 0;
+ +int main(int argc, const char *argv[]) {
+ +       int ret = printf("Hello world: %s\n", argv[0]);
+ +       return (ret > 0);
+<
+
+Ideally, we would like two commits here: one adding the argv parameter, and
+one checking the printf return value.
+
+One way to do so is to edit the file, deleting the return value code, stage,
+commit the argv feature; then, go back to source file, undo previous deletion,
+stage, and commit the return value feature.
+
+Another way is to edit the hunk from the magit buffer!
+
+Enter in edition mode with the mapping <kbd>E</kbd>, and start to edit the
+hunk, to remove the return value feature. After edition, you should have this
+result: >
+ -int main() {
+ -	printf("Hello world\n");
+ -	return 0;
+ +int main(int argc, const char *argv[]) {
+ +	printf("Hello world: %s\n", argv[0]);
+ +	return 0;
+<
+
+Stage the hunk, as is. Now you can see that you have the argv feature in
+staged section: >
+ -int main() {
+ -	printf("Hello world\n");
+ +int main(int argc, const char *argv[]) {
+ +	printf("Hello world: %s\n", argv[0]);
+<
+
+And that you have the return value feature in unstaged section: >
+ -	printf("Hello world: %s\n", argv[0]);
+ -	return 0;
+ +	int ret = printf("Hello world: %s\n", argv[0]);
+ +	return (ret > 0);
+<
+
+Voilà, you just did your first partial line staging!
 
 VISUAL SELECTION                                      *vimagit-visual-selection*
 
@@ -325,6 +371,13 @@ section only.
   <I>       Add the file under the cursor in .gitgnore
 
 
+                                    *vimagit-E*                *magit#edit_hunk*
+  <E>       Set the magit buffer in edit mode, allowing to edit a hunk before
+            staging it.
+            Edit mode is left after stage/unstage command, or a refresh
+            command.
+            See |vimagit-inline-modification| to learn how to use this
+            feature.
 
                                     *vimagit-J*                *magit#jump_to()*
                                     *vimagit-<C-]>*

plugin/magit.vim

@@ -30,6 +30,7 @@ let g:magit_auto_close             = get(g:, 'magit_auto_close',
 let g:magit_auto_foldopen            = get(g:, 'magit_auto_foldopen',               1)
 let g:magit_default_sections       = get(g:, 'magit_default_sections',          ['info', 'global_help', 'commit', 'staged', 'unstaged'])
 let g:magit_discard_untracked_do_delete = get(g:, 'magit_discard_untracked_do_delete',        0)
+let g:magit_default_editable       = get(g:, 'magit_default_editable',          0)
 
 let g:magit_refresh_gutter         = get(g:, 'magit_refresh_gutter'   ,         1)
 " Should deprecate the following
@@ -571,18 +572,6 @@ function! magit#update_buffer(...)
 	else
 		call s:set_mode_read()
 	endif
-	" FIXME: find a way to save folding state. According to help, this won't
-	" help:
-	" > This does not save fold information.
-	" Playing with foldenable around does not help.
-	" mkview does not help either.
-	let l:winview = winsaveview()
-
-	" remove all signs (needed as long as we wipe buffer)
-	call magit#sign#remove_all()
-
-	" delete buffer
-	silent! execute "silent :%delete _"
 
 	" be smart for the cursor position after refresh, if stage/unstaged
 	" occured
@@ -604,6 +593,21 @@ function! magit#update_buffer(...)
 		return
 	endif
 
+	setlocal modifiable
+
+	" FIXME: find a way to save folding state. According to help, this won't
+	" help:
+	" > This does not save fold information.
+	" Playing with foldenable around does not help.
+	" mkview does not help either.
+	let l:winview = winsaveview()
+
+	" remove all signs (needed as long as we wipe buffer)
+	call magit#sign#remove_all()
+
+	" delete buffer
+	silent! execute "silent :%delete _"
+
 	for section in g:magit_default_sections
 		try
 			let func = s:mg_display_functions[section]
@@ -620,6 +624,12 @@ function! magit#update_buffer(...)
 
 	call magit#utils#clear_undo()
 
+	if ( b:magit_editable )
+		setlocal modifiable
+	else
+		setlocal nomodifiable
+	endif
+
 	setlocal filetype=magit
 
 	if ( b:magit_current_commit_mode != '' && b:magit_commit_newly_open == 1 )
@@ -767,6 +777,8 @@ function! magit#show_magit(display, ...)
 		let b:magit_default_fold_level = a:2
 	endif
 
+	let b:magit_editable = g:magit_default_editable
+
 	setlocal buftype=nofile
 	setlocal bufhidden=hide
 	setlocal noswapfile
@@ -1091,6 +1103,15 @@ function! magit#mark_vselect() range
 	return <SID>mg_mark_lines_in_hunk(a:firstline, a:lastline)
 endfunction
 
+
+function! magit#edit_hunk()
+	let b:magit_editable = 1
+	setlocal modifiable
+	if exists(':AirlineRefresh')
+		execute "AirlineRefresh"
+	endif
+endfunction
+
 " magit#ignore_file: this function add the file under cursor to .gitignore
 " FIXME: git diff adds some strange characters to end of line
 function! magit#ignore_file() abort
@@ -1130,13 +1151,15 @@ function! magit#commit_command(mode)
 			" when we do commit, it is prefered ot commit the way we prepared it
 			" (.i.e normal or amend), whatever we commit with CC or CA.
 			call <SID>mg_git_commit(b:magit_current_commit_mode)
+			let b:magit_editable = 0
 			if exists('#User#VimagitLeaveCommit')
 				doautocmd User VimagitLeaveCommit
 			endif
 		else
 			let b:magit_current_commit_mode=a:mode
 			let b:magit_commit_newly_open=1
 			call s:set_mode_write()
+			let b:magit_editable = 1
 			setlocal nomodified
 		endif
 	endif
@@ -1263,7 +1286,9 @@ function! magit#show_version()
 endfunction
 
 function! magit#get_current_mode()
-	if ( b:magit_current_commit_mode == '' )
+	if ( b:magit_editable )
+		return "STAGING-EDIT"
+	elseif ( b:magit_current_commit_mode == '' )
 		return "STAGING"
 	elseif ( b:magit_current_commit_mode == 'CC' )
 		return "COMMIT"

test/addHunk.vader

@@ -56,6 +56,7 @@ Execute (Stage untracked file with magit#stage_hunk modified hunk):
     call Search_file('unstaged')
     call magit#open_close_folding(1)
     /^+
+    call magit#edit_hunk()
     call setline(line('.'), substitute(getline('.'), '^\(+.*\) .\{-\}$', '\1 vimatest', ''))
     call Cursor_position()
     call magit#stage_hunk(0)