[PATCH v2 14/24] builtin/init-db: add environment variable for new repo hash

From: brian m. carlson <sandals@crustytoothpaste.net>
Date: Feb 22, 2020, 20:17 UTC
Message-ID: <20200222201749.937983-15-sandals@crustytoothpaste.net>
In-Reply-To: <20200222201749.937983-1-sandals@crustytoothpaste.net>

For the foreseeable future, SHA-1 will be the default algorithm for Git. However, when running the testsuite, we want to be able to test an arbitrary algorithm. It would be quite burdensome and very untidy to have to specify the algorithm we'd like to test every time we initialized a new repository somewhere in the testsuite, so add an environment variable to allow us to specify the default hash algorithm for Git.

This has the benefit that we can set it once for the entire testsuite and not have to think about it. In the future, users can also use it to set the default for their repositories if they would like to do so.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
---
 Documentation/git.txt | 6 ++++++
 builtin/init-db.c     | 9 +++++++++
 2 files changed, 15 insertions(+)

diff --git a/Documentation/git.txt b/Documentation/git.txt
index b0672bd806..9d6769e95a 100644
--- a/Documentation/git.txt
+++ b/Documentation/git.txt
@@ -493,6 +493,12 @@ double-quotes and respecting backslash escapes. E.g., the value
 	details. This variable has lower precedence than other path
 	variables such as GIT_INDEX_FILE, GIT_OBJECT_DIRECTORY...
 
+`GIT_DEFAULT_HASH_ALGORITHM`::
+	If this variable is set, the default hash algorithm for new
+	repositories will be set to this value. This value is currently
+	ignored when cloning; the setting of the remote repository
+	is used instead. The default is "sha1".
+
 Git Commits
 ~~~~~~~~~~~
 `GIT_AUTHOR_NAME`::
diff --git a/builtin/init-db.c b/builtin/init-db.c
index d05552f0ae..ab4fd682ab 100644
--- a/builtin/init-db.c
+++ b/builtin/init-db.c
@@ -20,6 +20,8 @@
 #define TEST_FILEMODE 1
 #endif
 
+#define GIT_DEFAULT_HASH_ENVIRONMENT "GIT_DEFAULT_HASH"
+
 static int init_is_bare_repository = 0;
 static int init_shared_repository = -1;
 static const char *init_db_template_dir;
@@ -356,6 +358,7 @@ static void separate_git_dir(const char *git_dir, const char *git_link)
 
 static void validate_hash_algorithm(struct repository_format *repo_fmt, int hash)
 {
+	const char *env = getenv(GIT_DEFAULT_HASH_ENVIRONMENT);
 	/*
 	 * If we already have an initialized repo, don't allow the user to
 	 * specify a different algorithm, as that could cause corruption.
@@ -365,6 +368,12 @@ static void validate_hash_algorithm(struct repository_format *repo_fmt, int hash
 		die(_("attempt to reinitialize repository with different hash"));
 	else if (hash != GIT_HASH_UNKNOWN)
 		repo_fmt->hash_algo = hash;
+	else if (env) {
+		int env_algo = hash_algo_by_name(env);
+		if (env_algo == GIT_HASH_UNKNOWN)
+			die(_("unknown hash algorithm '%s'"), env);
+		repo_fmt->hash_algo = env_algo;
+	}
 }
 
 int init_db(const char *git_dir, const char *real_git_dir,