read-cache: let read-cache respect submodule ignore=all and --force

Given the submdule configuration is ignore=all then only update the
submdule if the --force option is given and the submodule is explicit
given in the pathspec.

A message is printed (like ignored files) guiding the user to use the
--force flag if the user has explicitely want to update the submodule
reference.

The reason for the change is support submodule branch tracking or
similar and git status state nothing and git add should not add either.
The workflow is more logic and similar to regular ignored files even
the submodule is already tracked.

The change opens up a lot of possibilities for submodules to be used
more freely and a like the repo tool. A submodule can be added for many
more reason and loosely coupled dependencies to the super repo which often
gives the friction of handle the explicit commits and updates without
the need for tracking the submodule sha1 by sha1.

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

Author: bicschneider

read-cache.c

@@ -48,6 +48,8 @@
 #include "csum-file.h"
 #include "promisor-remote.h"
 #include "hook.h"
+#include "submodule.h"
+#include "submodule-config.h"
 
 /* Mask for the name length in ce_flags in the on-disk index */
 
@@ -3927,13 +3929,55 @@ static void update_callback(struct diff_queue_struct *q,
 		default:
 			die(_("unexpected diff status %c"), p->status);
 		case DIFF_STATUS_MODIFIED:
-		case DIFF_STATUS_TYPE_CHANGED:
+		case DIFF_STATUS_TYPE_CHANGED: {
+			struct stat st;
+			if (!lstat(path, &st) && S_ISDIR(st.st_mode)) { // only consider submodule if it is a directory
+				const struct submodule *sub = submodule_from_path(data->repo, null_oid(the_hash_algo), path);
+				if (sub && sub->name && sub->ignore && !strcmp(sub->ignore, "all")) {
+					int pathspec_matches = 0;
+					char *norm_pathspec = NULL;
+					int ps_i;
+					trace_printf("ignore=all %s\n", path);
+					trace_printf("pathspec %s\n",
+							(data->pathspec && data->pathspec->nr) ? "has pathspec" : "no pathspec");
+					/* Safely scan all pathspec items (q->nr may exceed pathspec->nr). */
+					if (data->pathspec) {
+						for (ps_i = 0; ps_i < data->pathspec->nr; ps_i++) {
+							const char *m = data->pathspec->items[ps_i].match;
+							if (!m)
+								continue;
+							norm_pathspec = xstrdup(m);
+							strip_dir_trailing_slashes(norm_pathspec);
+							if (!strcmp(path, norm_pathspec)) {
+								pathspec_matches = 1;
+								FREE_AND_NULL(norm_pathspec);
+								break;
+							}
+							FREE_AND_NULL(norm_pathspec);
+						}
+					}
+					if (pathspec_matches) {
+						if (data->ignored_too && data->ignored_too > 0) {
+							trace_printf("Forcing add of submodule ignored=all due to --force: %s\n", path);
+						} else {
+							printf(_("Skipping submodule due to ignore=all: %s"), path);
+							printf(_("Use -f if you really want to add them.") );
+							continue;
+						}
+					} else {
+						/* No explicit pathspec match -> skip silently (or with trace). */
+						trace_printf("pathspec does not match %s\n", path);
+						continue;
+					}
+				}
+			}
 			if (add_file_to_index(data->index, path, data->flags)) {
 				if (!(data->flags & ADD_CACHE_IGNORE_ERRORS))
 					die(_("updating files failed"));
 				data->add_errors++;
 			}
 			break;
+		}
 		case DIFF_STATUS_DELETED:
 			if (data->flags & ADD_CACHE_IGNORE_REMOVAL)
 				break;