[PATCH] submodule: spell out API of submodule_move_head

[Stefan Beller <sbeller@google.com>]

This way users of this function do not need to read the implementation to
know what it will do.

Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Stefan Beller <sbeller@google.com>
---
 submodule.c |  5 -----
 submodule.h | 18 ++++++++++++++++++
 2 files changed, 18 insertions(+), 5 deletions(-)

diff --git a/submodule.c b/submodule.c
index c1edc91a13..d12e4ea96c 100644
--- a/submodule.c
+++ b/submodule.c
@@ -1507,11 +1507,6 @@ static void submodule_reset_index(const char *path)
 		die("could not reset submodule index");
 }
 
-/**
- * Moves a submodule at a given path from a given head to another new head.
- * For edge cases (a submodule coming into existence or removing a submodule)
- * pass NULL for old or new respectively.
- */
 int submodule_move_head(const char *path,
 			 const char *old,
 			 const char *new,
diff --git a/submodule.h b/submodule.h
index f0da0277a4..3c15977be9 100644
--- a/submodule.h
+++ b/submodule.h
@@ -111,6 +111,24 @@ extern void connect_work_tree_and_git_dir(const char *work_tree, const char *git
  */
 int submodule_to_gitdir(struct strbuf *buf, const char *submodule);
 
+/**
+ * Move the HEAD and content of the active submodule at 'path' from object id
+ * 'old' to 'new'.
+ *
+ * Updates the submodule at 'path' and files in its work tree to commit
+ * 'new'. The commit previously pointed to by the submodule is named by
+ * 'old'. This updates the submodule's HEAD, index, and work tree but
+ * does not touch its gitlink entry in the superproject.
+ *
+ * If the submodule did not previously exist, then 'old' should be NULL.
+ * Similarly, if the submodule is to be removed, 'new' should be NULL.
+ *
+ * If updating the submodule would cause local changes to be overwritten,
+ * then instead of updating the submodule, this function prints an error
+ * message and returns -1.
+ *
+ * If the submodule is not active, this does nothing and returns 0.
+ */
 #define SUBMODULE_MOVE_HEAD_DRY_RUN (1<<0)
 #define SUBMODULE_MOVE_HEAD_FORCE   (1<<1)
 extern int submodule_move_head(const char *path,
-- 
2.14.0.rc0.3.g6c2e499285