Documentation: update add --force option + ignore=all config

- git-add.adoc: Update the --force documentation for submodule behaviour
  to be added even the given configuration ignore=all.
- gitmodules.adoc and config/submodule.adoc: The submodule config
  ignore=all now need --force in order to update the index.

Signed-off-by: Claus Schneider(Eficode) <claus.schneider@eficode.com>

Author: bicschneider

Documentation/config/submodule.adoc

@@ -32,15 +32,16 @@ submodule.<name>.fetchRecurseSubmodules::
 
 submodule.<name>.ignore::
 	Defines under what circumstances "git status" and the diff family show
-	a submodule as modified. When set to "all", it will never be considered
-	modified (but it will nonetheless show up in the output of status and
-	commit when it has been staged), "dirty" will ignore all changes
-	to the submodule's work tree and
+	a submodule as modified.
+	Set to "all" will never considered the submodule modified. It can
+	nevertheless be staged using the option --force and it will then show up
+	in the output of status.
+	Set to "dirty" will ignore all changes to the submodule's work tree and
 	takes only differences between the HEAD of the submodule and the commit
 	recorded in the superproject into account. "untracked" will additionally
 	let submodules with modified tracked files in their work tree show up.
-	Using "none" (the default when this option is not set) also shows
-	submodules that have untracked files in their work tree as changed.
+	Set to "none"(default) It is also shows submodules that have untracked
+	files in their work tree as changed.
 	This setting overrides any setting made in .gitmodules for this submodule,
 	both settings can be overridden on the command line by using the
 	"--ignore-submodules" option. The 'git submodule' commands are not

Documentation/git-add.adoc

@@ -77,7 +77,10 @@ in linkgit:gitglossary[7].
 
 `-f`::
 `--force`::
-	Allow adding otherwise ignored files.
+	Allow adding otherwise ignored files. The option is also used when
+	`submodule.<name>.ignore=all` is set, but you want to stage an
+	update of the submodule. The `path` to the submodule must be explicitly
+	specified.
 
 `--sparse`::
 	Allow updating index entries outside of the sparse-checkout cone.

Documentation/gitmodules.adoc

@@ -70,7 +70,10 @@ submodule.<name>.ignore::
 --
 	all;; The submodule will never be considered modified (but will
 	    nonetheless show up in the output of status and commit when it has
-	    been staged).
+	    been staged). Add `(new commits)` can be overruled using the
+	    `git add --force <submodule.path>`.
+		The setting affects `status`, `update-index`, `diff` and `log`(due
+		to underlaying `diff`).
 
 	dirty;; All changes to the submodule's work tree will be ignored, only
 	    committed differences between the `HEAD` of the submodule and its