environment: guard state depending on a repository

In "environment.h" we have quite a lot of functions and variables that
either explicitly or implicitly depend on `the_repository`.

The implicit set of stateful declarations includes for example variables
which get populated when parsing a repository's Git configuration. This
set of variables is broken by design, as their state often depends on
the last repository config that has been parsed. So they may or may not
represent the state of `the_repository`.

Fixing that is quite a big undertaking, and later patches in this series
will demonstrate a solution for a first small set of those variables. So
for now, let's guard these with `USE_THE_REPOSITORY_VARIABLE` so that
callers are aware of the implicit dependency.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

14 files changed, 53 insertions, 1 deletions

diff --git a/compat/mingw.c b/compat/mingw.c
index 29d3f09768..5c2080c04c 100644
--- a/compat/mingw.c
+++ b/compat/mingw.c
@@ -1,3 +1,5 @@
+#define USE_THE_REPOSITORY_VARIABLE
+
 #include "../git-compat-util.h"
 #include "win32.h"
 #include <aclapi.h>
diff --git a/compat/win32/path-utils.c b/compat/win32/path-utils.c
index b658ca3f81..966ef779b9 100644
--- a/compat/win32/path-utils.c
+++ b/compat/win32/path-utils.c
@@ -1,3 +1,5 @@
+#define USE_THE_REPOSITORY_VARIABLE
+
 #include "../../git-compat-util.h"
 #include "../../environment.h"
 
diff --git a/config.c b/config.c
index 043e1c8a07..f3066c3747 100644
--- a/config.c
+++ b/config.c
@@ -6,6 +6,8 @@
  *
  */
 
+#define USE_THE_REPOSITORY_VARIABLE
+
 #include "git-compat-util.h"
 #include "abspath.h"
 #include "advice.h"
diff --git a/environment.h b/environment.h
index f1a7c645db..934859e1c5 100644
--- a/environment.h
+++ b/environment.h
@@ -102,6 +102,28 @@ int use_optional_locks(void);
 const char *get_git_namespace(void);
 const char *strip_namespace(const char *namespaced_ref);
 
+/*
+ * TODO: All the below state either explicitly or implicitly relies on
+ * `the_repository`. We should eventually get rid of these and make the
+ * dependency on a repository explicit:
+ *
+ *   - `setup_git_env()` ideally shouldn't exist as it modifies global state,
+ *     namely the environment. The current process shouldn't ever access that
+ *     state via envvars though, but should instead consult a `struct
+ *     repository`. When spawning new processes, we would ideally also pass a
+ *     `struct repository` and then set up the environment variables for the
+ *     child process, only.
+ *
+ *   - `have_git_dir()` should not have to exist at all. Instead, we should
+ *     decide on whether or not we have a `struct repository`.
+ *
+ *   - All the global config variables should become tied to a repository. Like
+ *     this, we'd correctly honor repository-local configuration and be able to
+ *     distinguish configuration values from different repositories.
+ *
+ * Please do not add new global config variables here.
+ */
+# ifdef USE_THE_REPOSITORY_VARIABLE
 void setup_git_env(const char *git_dir);
 
 /*
@@ -213,4 +235,5 @@ extern const char *comment_line_str;
 extern char *comment_line_str_to_free;
 extern int auto_comment_line_char;
 
-#endif
+# endif /* USE_THE_REPOSITORY_VARIABLE */
+#endif /* ENVIRONMENT_H */
diff --git a/name-hash.c b/name-hash.c
index 3a58ce03d9..95528e3bcd 100644
--- a/name-hash.c
+++ b/name-hash.c
@@ -5,6 +5,9 @@
  *
  * Copyright (C) 2008 Linus Torvalds
  */
+
+#define USE_THE_REPOSITORY_VARIABLE
+
 #include "git-compat-util.h"
 #include "environment.h"
 #include "gettext.h"
diff --git a/path.c b/path.c
index a3bf25b7de..93491bab14 100644
--- a/path.c
+++ b/path.c
@@ -2,6 +2,8 @@
  * Utilities for paths and pathnames
  */
 
+#define USE_THE_REPOSITORY_VARIABLE
+
 #include "git-compat-util.h"
 #include "abspath.h"
 #include "environment.h"
diff --git a/preload-index.c b/preload-index.c
index 63fd35d64b..7926eb09a6 100644
--- a/preload-index.c
+++ b/preload-index.c
@@ -1,6 +1,9 @@
 /*
  * Copyright (C) 2008 Linus Torvalds
  */
+
+#define USE_THE_REPOSITORY_VARIABLE
+
 #include "git-compat-util.h"
 #include "pathspec.h"
 #include "dir.h"
diff --git a/prompt.c b/prompt.c
index 8935fe4dfb..f21c5bf1c7 100644
--- a/prompt.c
+++ b/prompt.c
@@ -1,3 +1,5 @@
+#define USE_THE_REPOSITORY_VARIABLE
+
 #include "git-compat-util.h"
 #include "parse.h"
 #include "environment.h"
diff --git a/refs/files-backend.c b/refs/files-backend.c
index 1cff65f6ae..1bbb550f3a 100644
--- a/refs/files-backend.c
+++ b/refs/files-backend.c
@@ -1,3 +1,5 @@
+#define USE_THE_REPOSITORY_VARIABLE
+
 #include "../git-compat-util.h"
 #include "../copy.h"
 #include "../environment.h"
diff --git a/sparse-index.c b/sparse-index.c
index 9958656ded..542ca5f411 100644
--- a/sparse-index.c
+++ b/sparse-index.c
@@ -1,3 +1,5 @@
+#define USE_THE_REPOSITORY_VARIABLE
+
 #include "git-compat-util.h"
 #include "environment.h"
 #include "gettext.h"
diff --git a/statinfo.c b/statinfo.c
index 3c6bc049c1..30a164b0e6 100644
--- a/statinfo.c
+++ b/statinfo.c
@@ -1,3 +1,5 @@
+#define USE_THE_REPOSITORY_VARIABLE
+
 #include "git-compat-util.h"
 #include "environment.h"
 #include "statinfo.h"
diff --git a/t/helper/test-path-utils.c b/t/helper/test-path-utils.c
index bf0e23ed50..f57c8d706a 100644
--- a/t/helper/test-path-utils.c
+++ b/t/helper/test-path-utils.c
@@ -1,3 +1,5 @@
+#define USE_THE_REPOSITORY_VARIABLE
+
 #include "test-tool.h"
 #include "abspath.h"
 #include "environment.h"
diff --git a/tree-diff.c b/tree-diff.c
index 9252481df3..5eab8af631 100644
--- a/tree-diff.c
+++ b/tree-diff.c
@@ -1,6 +1,9 @@
 /*
  * Helper functions for tree diff generation
  */
+
+#define USE_THE_REPOSITORY_VARIABLE
+
 #include "git-compat-util.h"
 #include "diff.h"
 #include "diffcore.h"
diff --git a/userdiff.c b/userdiff.c
index 989629149f..d43d8360d1 100644
--- a/userdiff.c
+++ b/userdiff.c
@@ -1,3 +1,5 @@
+#define USE_THE_REPOSITORY_VARIABLE
+
 #include "git-compat-util.h"
 #include "config.h"
 #include "userdiff.h"