Merge branch 'jc/attr-tree-config'

The attribute subsystem learned to honor `attr.tree` configuration
that specifies which tree to read the .gitattributes files from.

* jc/attr-tree-config:
  attr: add attr.tree for setting the treeish to read attributes from
  attr: read attributes from HEAD when bare repo

7 files changed, 119 insertions, 3 deletions

diff --git a/Documentation/config.txt b/Documentation/config.txt
index b1dba1ae85..e3a74dd1c1 100644
--- a/Documentation/config.txt
+++ b/Documentation/config.txt
@@ -371,6 +371,8 @@ other popular tools, and describe them in your documentation.
 
 include::config/advice.txt[]
 
+include::config/attr.txt[]
+
 include::config/core.txt[]
 
 include::config/add.txt[]
diff --git a/Documentation/config/attr.txt b/Documentation/config/attr.txt
new file mode 100644
index 0000000000..1a482d6af2
--- /dev/null
+++ b/Documentation/config/attr.txt
@@ -0,0 +1,7 @@
+attr.tree::
+	A reference to a tree in the repository from which to read attributes,
+	instead of the `.gitattributes` file in the working tree. In a bare
+	repository, this defaults to `HEAD:.gitattributes`. If the value does
+	not resolve to a valid tree object, an empty tree is used instead.
+	When the `GIT_ATTR_SOURCE` environment variable or `--attr-source`
+	command line option are used, this configuration variable has no effect.
diff --git a/attr.c b/attr.c
index 3c0b4fb3d9..e62876dfd3 100644
--- a/attr.c
+++ b/attr.c
@@ -7,7 +7,7 @@
  */
 
 #include "git-compat-util.h"
-#include "parse.h"
+#include "config.h"
 #include "environment.h"
 #include "exec-cmd.h"
 #include "attr.h"
@@ -24,6 +24,8 @@
 #include "tree-walk.h"
 #include "object-name.h"
 
+const char *git_attr_tree;
+
 const char git_attr__true[] = "(builtin)true";
 const char git_attr__false[] = "\0(builtin)false";
 static const char git_attr__unknown[] = "(builtin)unknown";
@@ -1194,6 +1196,7 @@ static void collect_some_attrs(struct index_state *istate,
 }
 
 static const char *default_attr_source_tree_object_name;
+static int ignore_bad_attr_tree;
 
 void set_git_attr_source(const char *tree_object_name)
 {
@@ -1205,10 +1208,24 @@ static void compute_default_attr_source(struct object_id *attr_source)
 	if (!default_attr_source_tree_object_name)
 		default_attr_source_tree_object_name = getenv(GIT_ATTR_SOURCE_ENVIRONMENT);
 
+	if (!default_attr_source_tree_object_name && git_attr_tree) {
+		default_attr_source_tree_object_name = git_attr_tree;
+		ignore_bad_attr_tree = 1;
+	}
+
+	if (!default_attr_source_tree_object_name &&
+	    startup_info->have_repository &&
+	    is_bare_repository()) {
+		default_attr_source_tree_object_name = "HEAD";
+		ignore_bad_attr_tree = 1;
+	}
+
 	if (!default_attr_source_tree_object_name || !is_null_oid(attr_source))
 		return;
 
-	if (repo_get_oid_treeish(the_repository, default_attr_source_tree_object_name, attr_source))
+	if (repo_get_oid_treeish(the_repository,
+				 default_attr_source_tree_object_name,
+				 attr_source) && !ignore_bad_attr_tree)
 		die(_("bad --attr-source or GIT_ATTR_SOURCE"));
 }
 
diff --git a/attr.h b/attr.h
index 2b745df405..127998ae01 100644
--- a/attr.h
+++ b/attr.h
@@ -236,4 +236,6 @@ const char *git_attr_global_file(void);
 /* Return whether the system gitattributes file is enabled and should be used. */
 int git_attr_system_is_enabled(void);
 
+extern const char *git_attr_tree;
+
 #endif /* ATTR_H */
diff --git a/config.c b/config.c
index f9a1cca4e8..b330c7adb4 100644
--- a/config.c
+++ b/config.c
@@ -19,6 +19,7 @@
 #include "repository.h"
 #include "lockfile.h"
 #include "mailmap.h"
+#include "attr.h"
 #include "exec-cmd.h"
 #include "strbuf.h"
 #include "quote.h"
@@ -1760,6 +1761,18 @@ static int git_default_mailmap_config(const char *var, const char *value)
 	return 0;
 }
 
+static int git_default_attr_config(const char *var, const char *value)
+{
+	if (!strcmp(var, "attr.tree"))
+		return git_config_string(&git_attr_tree, var, value);
+
+	/*
+	 * Add other attribute related config variables here and to
+	 * Documentation/config/attr.txt.
+	 */
+	return 0;
+}
+
 int git_default_config(const char *var, const char *value,
 		       const struct config_context *ctx, void *cb)
 {
@@ -1783,6 +1796,9 @@ int git_default_config(const char *var, const char *value,
 	if (starts_with(var, "mailmap."))
 		return git_default_mailmap_config(var, value);
 
+	if (starts_with(var, "attr."))
+		return git_default_attr_config(var, value);
+
 	if (starts_with(var, "advice.") || starts_with(var, "color.advice"))
 		return git_default_advice_config(var, value);
 
diff --git a/t/t0003-attributes.sh b/t/t0003-attributes.sh
index 26e082f05b..ecf43ab545 100755
--- a/t/t0003-attributes.sh
+++ b/t/t0003-attributes.sh
@@ -40,6 +40,10 @@ attr_check_source () {
 	test_cmp expect actual &&
 	test_must_be_empty err
 
+	git $git_opts -c "attr.tree=$source" check-attr test -- "$path" >actual 2>err &&
+	test_cmp expect actual &&
+	test_must_be_empty err
+
 	GIT_ATTR_SOURCE="$source" git $git_opts check-attr test -- "$path" >actual 2>err &&
 	test_cmp expect actual &&
 	test_must_be_empty err
@@ -342,6 +346,74 @@ test_expect_success 'bare repository: check that .gitattribute is ignored' '
 	)
 '
 
+bad_attr_source_err="fatal: bad --attr-source or GIT_ATTR_SOURCE"
+
+test_expect_success '--attr-source is bad' '
+	test_when_finished rm -rf empty &&
+	git init empty &&
+	(
+		cd empty &&
+		echo "$bad_attr_source_err" >expect_err &&
+		test_must_fail git --attr-source=HEAD check-attr test -- f/path 2>err &&
+		test_cmp expect_err err
+	)
+'
+
+test_expect_success 'attr.tree when HEAD is unborn' '
+	test_when_finished rm -rf empty &&
+	git init empty &&
+	(
+		cd empty &&
+		echo "f/path: test: unspecified" >expect &&
+		git -c attr.tree=HEAD check-attr test -- f/path >actual 2>err &&
+		test_must_be_empty err &&
+		test_cmp expect actual
+	)
+'
+
+test_expect_success 'bad attr source defaults to reading .gitattributes file' '
+	test_when_finished rm -rf empty &&
+	git init empty &&
+	(
+		cd empty &&
+		echo "f/path test=val" >.gitattributes &&
+		echo "f/path: test: val" >expect &&
+		git -c attr.tree=HEAD check-attr test -- f/path >actual 2>err &&
+		test_must_be_empty err &&
+		test_cmp expect actual
+	)
+'
+
+test_expect_success 'bare repo defaults to reading .gitattributes from HEAD' '
+	test_when_finished rm -rf test bare_with_gitattribute &&
+	git init test &&
+	test_commit -C test gitattributes .gitattributes "f/path test=val" &&
+	git clone --bare test bare_with_gitattribute &&
+	echo "f/path: test: val" >expect &&
+	git -C bare_with_gitattribute check-attr test -- f/path >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'precedence of --attr-source, GIT_ATTR_SOURCE, then attr.tree' '
+	test_when_finished rm -rf empty &&
+	git init empty &&
+	(
+		cd empty &&
+		git checkout -b attr-source &&
+		test_commit "val1" .gitattributes "f/path test=val1" &&
+		git checkout -b attr-tree &&
+		test_commit "val2" .gitattributes "f/path test=val2" &&
+		git checkout attr-source &&
+		echo "f/path: test: val1" >expect &&
+		GIT_ATTR_SOURCE=attr-source git -c attr.tree=attr-tree --attr-source=attr-source \
+		check-attr test -- f/path >actual &&
+		test_cmp expect actual &&
+		GIT_ATTR_SOURCE=attr-source git -c attr.tree=attr-tree \
+		check-attr test -- f/path >actual &&
+		test_cmp expect actual
+	)
+'
+
 test_expect_success 'bare repository: with --source' '
 	(
 		cd bare.git &&
diff --git a/t/t5001-archive-attr.sh b/t/t5001-archive-attr.sh
index 0ff47a239d..eaf959d8f6 100755
--- a/t/t5001-archive-attr.sh
+++ b/t/t5001-archive-attr.sh
@@ -138,7 +138,7 @@ test_expect_success 'git archive with worktree attributes, bare' '
 '
 
 test_expect_missing	bare-worktree/ignored
-test_expect_exists	bare-worktree/ignored-by-tree
+test_expect_missing	bare-worktree/ignored-by-tree
 test_expect_exists	bare-worktree/ignored-by-worktree
 
 test_expect_success 'export-subst' '