[PATCH v3 4/9] tree: handle submodule case for read_tree_at properly

["Heather Lapointe via GitGitGadget" <gitgitgadget@gmail.com>]

From: Heather Lapointe <alpha@alphaservcomputing.solutions>

This supports traversal into an actual submodule for read_tree_at.
The logic is blocked on pathspec->recurse_submodules now,
but previously hadn't been executed due to all fn() cases
returning early for submodules.

Signed-off-by: Heather Lapointe <alpha@alphaservcomputing.solutions>
---
 tree.c | 88 ++++++++++++++++++++++++++++++++++++++++------------------
 1 file changed, 61 insertions(+), 27 deletions(-)

diff --git a/tree.c b/tree.c
index 13f9173d45e..2a087c010f9 100644
--- a/tree.c
+++ b/tree.c
@@ -8,6 +8,7 @@
 #include "alloc.h"
 #include "tree-walk.h"
 #include "repository.h"
+#include "pathspec.h"
 
 const char *tree_type = "tree";
 
@@ -47,40 +48,73 @@ int read_tree_at(struct repository *r,
 			return -1;
 		}
 
-		if (S_ISDIR(entry.mode))
+		if (S_ISDIR(entry.mode)) {
 			oidcpy(&oid, &entry.oid);
-		else if (S_ISGITLINK(entry.mode)) {
-			struct commit *commit;
 
-			commit = lookup_commit(r, &entry.oid);
+			len = tree_entry_len(&entry);
+			strbuf_add(base, entry.path, len);
+			strbuf_addch(base, '/');
+			retval = read_tree_at(r, lookup_tree(r, &oid),
+						base, pathspec,
+						fn, context);
+			strbuf_setlen(base, oldlen);
+			if (retval)
+				return -1;
+		} else if (pathspec->recurse_submodules && S_ISGITLINK(entry.mode)) {
+			struct commit *commit;
+			struct repository subrepo;
+			struct repository* subrepo_p = &subrepo;
+			struct tree* submodule_tree;
+			char *submodule_rel_path;
+			int name_base_len = 0;
+
+			len = tree_entry_len(&entry);
+			strbuf_add(base, entry.path, len);
+			submodule_rel_path = base->buf;
+			// repo_submodule_init expects a path relative to submodule_prefix
+			if (r->submodule_prefix) {
+				name_base_len = strlen(r->submodule_prefix);
+				// we should always expect to start with submodule_prefix
+				assert(!strncmp(submodule_rel_path, r->submodule_prefix, name_base_len));
+				// strip the prefix
+				submodule_rel_path += name_base_len;
+				// if submodule_prefix doesn't end with a /, we want to get rid of that too
+				if (is_dir_sep(submodule_rel_path[0])) {
+					submodule_rel_path++;
+				}
+			}
+
+			if (repo_submodule_init(subrepo_p, r, submodule_rel_path, null_oid()))
+				die("couldn't init submodule %s", base->buf);
+
+			if (repo_read_index(subrepo_p) < 0)
+				die("index file corrupt");
+
+			commit = lookup_commit(subrepo_p, &entry.oid);
 			if (!commit)
-				die("Commit %s in submodule path %s%s not found",
+				die("Commit %s in submodule path %s not found",
 				    oid_to_hex(&entry.oid),
-				    base->buf, entry.path);
-
-			// FIXME: This is the wrong repo instance (it refers to the superproject)
-			// it will always fail as is (will fix in later patch)
-			// This current codepath isn't executed by any existing callbacks
-			// so it wouldn't show up as an issue at this time.
-			if (repo_parse_commit(r, commit))
-				die("Invalid commit %s in submodule path %s%s",
+				    base->buf);
+
+			if (repo_parse_commit(subrepo_p, commit))
+				die("Invalid commit %s in submodule path %s",
 				    oid_to_hex(&entry.oid),
-				    base->buf, entry.path);
+				    base->buf);
 
-			oidcpy(&oid, get_commit_tree_oid(commit));
-		}
-		else
-			continue;
+			submodule_tree = repo_get_commit_tree(subrepo_p, commit);
+			oidcpy(&oid, submodule_tree ? &submodule_tree->object.oid : NULL);
 
-		len = tree_entry_len(&entry);
-		strbuf_add(base, entry.path, len);
-		strbuf_addch(base, '/');
-		retval = read_tree_at(r, lookup_tree(r, &oid),
-				      base, pathspec,
-				      fn, context);
-		strbuf_setlen(base, oldlen);
-		if (retval)
-			return -1;
+			strbuf_addch(base, '/');
+
+			retval = read_tree_at(subrepo_p, lookup_tree(subrepo_p, &oid),
+						base, pathspec,
+						fn, context);
+			if (retval)
+			    die("failed to read tree for %s", base->buf);
+			strbuf_setlen(base, oldlen);
+			repo_clear(subrepo_p);
+		}
+		// else, this is a file (or a submodule, but no pathspec->recurse_submodules)
 	}
 	return 0;
 }
-- 
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