core: allow users to configure home directory

Some callers -- like our test suite and the test suites of our language
bindings -- want to isolate the home directory to avoid accidentally
including the executing user's actual home directory data.

Previously, we combined the notion of a home directory and global
configuration -- now that this is separated, we provide users the
ability to configure both.

include/git2/common.h

@@ -222,7 +222,9 @@ typedef enum {
 	GIT_OPT_GET_EXTENSIONS,
 	GIT_OPT_SET_EXTENSIONS,
 	GIT_OPT_GET_OWNER_VALIDATION,
-	GIT_OPT_SET_OWNER_VALIDATION
+	GIT_OPT_SET_OWNER_VALIDATION,
+	GIT_OPT_GET_HOMEDIR,
+	GIT_OPT_SET_HOMEDIR
 } git_libgit2_opt_t;
 
 /**
@@ -468,6 +470,16 @@ typedef enum {
  *      > Set that repository directories should be owned by the current
  *      > user. The default is to validate ownership.
  *
+ *   opts(GIT_OPT_GET_HOMEDIR, git_buf *out)
+ *      > Gets the current user's home directory, as it will be used
+ *      > for file lookups. The path is written to the `out` buffer.
+ *
+ *   opts(GIT_OPT_SET_HOMEDIR, const char *path)
+ *      > Sets the directory used as the current user's home directory,
+ *      > for file lookups.
+ *      >
+ *      > - `path` directory of home directory.
+ *
  * @param option Option key
  * @param ... value to set the option
  * @return 0 on success, <0 on failure

src/libgit2/libgit2.c

@@ -414,6 +414,25 @@ int git_libgit2_opts(int key, ...)
 		git_repository__validate_ownership = (va_arg(ap, int) != 0);
 		break;
 
+	case GIT_OPT_GET_HOMEDIR:
+		{
+			git_buf *out = va_arg(ap, git_buf *);
+			git_str str = GIT_STR_INIT;
+			const git_str *tmp;
+
+			if ((error = git_buf_tostr(&str, out)) < 0 ||
+			    (error = git_sysdir_get(&tmp, GIT_SYSDIR_HOME)) < 0 ||
+			    (error = git_str_put(&str, tmp->ptr, tmp->size)) < 0)
+				break;
+
+			error = git_buf_fromstr(out, &str);
+		}
+		break;
+
+	case GIT_OPT_SET_HOMEDIR:
+		error = git_sysdir_set(GIT_SYSDIR_HOME, va_arg(ap, const char *));
+		break;
+
 	default:
 		git_error_set(GIT_ERROR_INVALID, "invalid option key");
 		error = -1;