[PATCH 2/3] replace-objects: create wrapper around setting

From: Derrick Stolee via GitGitGadget <gitgitgadget@gmail.com>
Date: May 26, 2023, 18:43 UTC
Message-ID: <5fc2f923d9e6aa13781d7d6567c9bd38a9dd1f0e.1685126618.git.gitgitgadget@gmail.com>
In-Reply-To: <pull.1537.git.1685126617.gitgitgadget@gmail.com>

From: Derrick Stolee <derrickstolee@github.com>

The 'read_replace_objects' constant is initialized by git_default_config (if core.useReplaceRefs is disabled) and within setup_git_env (if GIT_NO_REPLACE_OBJECTS) is set. To ensure that this variable cannot be set accidentally in other places, wrap it in a replace_refs_enabled() method.

This allows us to remove the global from being recognized outside of replace-objects.c.

Further, a future change will help prevent the variable from being read before it is initialized. Centralizing its access is an important first step.

Signed-off-by: Derrick Stolee <derrickstolee@github.com>
---
 commit-graph.c   |  4 +---
 environment.c    |  1 -
 log-tree.c       |  2 +-
 replace-object.c |  7 +++++++
 replace-object.h | 15 ++++++++++++++-
 5 files changed, 23 insertions(+), 6 deletions(-)

diff --git a/commit-graph.c b/commit-graph.c
index 43558b4d9b0..95873317bf7 100644
--- a/commit-graph.c
+++ b/commit-graph.c
@@ -203,14 +203,12 @@ static struct commit_graph *alloc_commit_graph(void)
 	return g;
 }
 
-extern int read_replace_refs;
-
 static int commit_graph_compatible(struct repository *r)
 {
 	if (!r->gitdir)
 		return 0;
 
-	if (read_replace_refs) {
+	if (replace_refs_enabled(r)) {
 		prepare_replace_object(r);
 		if (hashmap_get_size(&r->objects->replace_map->map))
 			return 0;
diff --git a/environment.c b/environment.c
index 3b4d87c322f..e198b48081a 100644
--- a/environment.c
+++ b/environment.c
@@ -63,7 +63,6 @@ const char *editor_program;
 const char *askpass_program;
 const char *excludes_file;
 enum auto_crlf auto_crlf = AUTO_CRLF_FALSE;
-int read_replace_refs = 1;
 enum eol core_eol = EOL_UNSET;
 int global_conv_flags_eol = CONV_EOL_RNDTRP_WARN;
 char *check_roundtrip_encoding = "SHIFT-JIS";
diff --git a/log-tree.c b/log-tree.c
index 143b86fecf9..86212af3626 100644
--- a/log-tree.c
+++ b/log-tree.c
@@ -155,7 +155,7 @@ static int add_ref_decoration(const char *refname, const struct object_id *oid,
 
 	if (starts_with(refname, git_replace_ref_base)) {
 		struct object_id original_oid;
-		if (!read_replace_refs)
+		if (!replace_refs_enabled(the_repository))
 			return 0;
 		if (get_oid_hex(refname + strlen(git_replace_ref_base),
 				&original_oid)) {
diff --git a/replace-object.c b/replace-object.c
index ceec81c940c..cf91c3ba456 100644
--- a/replace-object.c
+++ b/replace-object.c
@@ -85,7 +85,14 @@ const struct object_id *do_lookup_replace_object(struct repository *r,
 	die(_("replace depth too high for object %s"), oid_to_hex(oid));
 }
 
+static int read_replace_refs = 1;
+
 void disable_replace_refs(void)
 {
 	read_replace_refs = 0;
 }
+
+int replace_refs_enabled(struct repository *r)
+{
+	return read_replace_refs;
+}
diff --git a/replace-object.h b/replace-object.h
index 7786d4152b0..b141075023e 100644
--- a/replace-object.h
+++ b/replace-object.h
@@ -27,6 +27,19 @@ void prepare_replace_object(struct repository *r);
 const struct object_id *do_lookup_replace_object(struct repository *r,
 						 const struct object_id *oid);
 
+
+/*
+ * Some commands disable replace-refs unconditionally, and otherwise each
+ * repository could alter the core.useReplaceRefs config value.
+ *
+ * Return 1 if and only if all of the following are true:
+ *
+ *  a. disable_replace_refs() has not been called.
+ *  b. GIT_NO_REPLACE_OBJECTS is unset or zero.
+ *  c. the given repository does not have core.useReplaceRefs=false.
+ */
+int replace_refs_enabled(struct repository *r);
+
 /*
  * If object sha1 should be replaced, return the replacement object's
  * name (replaced recursively, if necessary).  The return value is
@@ -41,7 +54,7 @@ const struct object_id *do_lookup_replace_object(struct repository *r,
 static inline const struct object_id *lookup_replace_object(struct repository *r,
 							    const struct object_id *oid)
 {
-	if (!read_replace_refs ||
+	if (!replace_refs_enabled(r) ||
 	    (r->objects->replace_map_initialized &&
 	     r->objects->replace_map->map.tablesize == 0))
 		return oid;

-- 
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