Get user's home dir in UTF-16 clean manner

On Windows, we are having problems with home directories
that have non-ascii characters in them.  This rewrites the
relevant code to fetch environment variables as UTF-16 and
then explicitly map then into UTF-8 for our internal usage.

src/fileops.c

@@ -345,13 +345,48 @@ int git_futils_rmdir_r(const char *path, git_directory_removal_type removal_type
 	return error;
 }
 
+#ifdef GIT_WIN32
+static char *win32_getenv(const wchar_t *name)
+{
+	char *val_utf8;
+	wchar_t *val_utf16;
+	DWORD len = GetEnvironmentVariableW(name, NULL, 0);
+
+	if (len <= 0)
+		return NULL;
+
+	val_utf16 = git__calloc(len, sizeof(wchar_t));
+	if (!val_utf16)
+		return NULL;
+
+	if (GetEnvironmentVariableW(name, val_utf16, len) != len - 1) {
+		giterr_set(GITERR_OS, "Could not read environment variable");
+		git__free(val_utf16);
+		return NULL;
+	}
+
+	val_utf8 = gitwin_from_utf16(val_utf16);
+
+	git__free(val_utf16);
+
+	return val_utf8;
+}
+#endif
+
 int git_futils_find_global_file(git_buf *path, const char *filename)
 {
-	const char *home = getenv("HOME");
+	char *home;
 
 #ifdef GIT_WIN32
-	if (home == NULL)
-		home = getenv("USERPROFILE");
+	home = win32_getenv(L"HOME");
+
+	if (!home)
+		home = win32_getenv(L"USERPROFILE");
+
+	if (home)
+		git_path_mkposix(home);
+#else
+	home = getenv("HOME");
 #endif
 
 	if (home == NULL) {
@@ -363,6 +398,10 @@ int git_futils_find_global_file(git_buf *path, const char *filename)
 	if (git_buf_joinpath(path, home, filename) < 0)
 		return -1;
 
+#ifdef GIT_WIN32
+	git__free(home);
+#endif
+
 	if (git_path_exists(path->ptr) == false) {
 		git_buf_clear(path);
 		return GIT_ENOTFOUND;

tests-clar/core/env.c

+#include "clar_libgit2.h"
+#include "fileops.h"
+#include "path.h"
+
+#ifdef GIT_WIN32
+
+#include "win32/utf-conv.h"
+
+static char *cl_getenv(const char *name)
+{
+	wchar_t *name_utf16 = gitwin_to_utf16(name);
+	DWORD value_len, alloc_len;
+	wchar_t *value_utf16;
+	char *value_utf8;
+
+	cl_assert(name_utf16);
+	alloc_len = GetEnvironmentVariableW(name_utf16, NULL, 0);
+	if (alloc_len < 0)
+		return NULL;
+	cl_assert(value_utf16 = git__calloc(alloc_len, sizeof(wchar_t)));
+	value_len = GetEnvironmentVariableW(name_utf16, value_utf16, alloc_len);
+	cl_assert_equal_i(value_len, alloc_len - 1);
+	cl_assert(value_utf8 = gitwin_from_utf16(value_utf16));
+	git__free(value_utf16);
+
+	return value_utf8;
+}
+
+static int cl_setenv(const char *name, const char *value)
+{
+	wchar_t *name_utf16 = gitwin_to_utf16(name);
+	wchar_t *value_utf16 = value ? gitwin_to_utf16(value) : NULL;
+
+	cl_assert(name_utf16);
+	cl_assert(SetEnvironmentVariableW(name_utf16, value_utf16));
+
+	git__free(name_utf16);
+	git__free(value_utf16);
+
+	return 0;
+
+}
+#else
+
+#include <stdlib.h>
+#define cl_getenv(n)   getenv(n)
+#define cl_setenv(n,v) (v) ? setenv((n),(v),1) : unsetenv(n)
+
+#endif
+
+static char *env_home = NULL;
+#ifdef GIT_WIN32
+static char *env_userprofile = NULL;
+#endif
+
+void test_core_env__initialize(void)
+{
+	env_home = cl_getenv("HOME");
+#ifdef GIT_WIN32
+	env_userprofile = cl_getenv("USERPROFILE");
+#endif
+}
+
+void test_core_env__cleanup(void)
+{
+	cl_setenv("HOME", env_home);
+#ifdef GIT_WIN32
+	cl_setenv("USERPROFILE", env_userprofile);
+
+	git__free(env_home);
+	git__free(env_userprofile);
+#endif
+}
+
+void test_core_env__0(void)
+{
+	static char *home_values[] = {
+		"fake_home",
+		"fáke_hõme", /* all in latin-1 supplement */
+		"fĀke_Ĥome", /* latin extended */
+		"fακε_hοmέ",  /* having fun with greek */
+		"faงe_นome", /* now I have no idea, but thai characters */
+		"f\xe1\x9cx80ke_\xe1\x9c\x91ome", /* tagalog characters */
+		"\xe1\xb8\x9fẢke_hoṁe", /* latin extended additional */
+		"\xf0\x9f\x98\x98\xf0\x9f\x98\x82", /* emoticons */
+		NULL
+	};
+	git_buf path = GIT_BUF_INIT, found = GIT_BUF_INIT;
+	char **val;
+	char *check;
+
+	for (val = home_values; *val != NULL; val++) {
+
+		if (p_mkdir(*val, 0777) == 0) {
+			/* if we can't make the directory, let's just assume
+			 * we are on a filesystem that doesn't support the
+			 * characters in question and skip this test...
+			 */
+			cl_git_pass(git_path_prettify(&path, *val, NULL));
+
+			cl_git_pass(cl_setenv("HOME", path.ptr));
+
+			/* do a quick check that it was set correctly */
+			check = cl_getenv("HOME");
+			cl_assert_equal_s(path.ptr, check);
+#ifdef GIT_WIN32
+			git__free(check);
+
+			cl_git_pass(cl_setenv("USERPROFILE", path.ptr));
+
+			/* do a quick check that it was set correctly */
+			check = cl_getenv("USERPROFILE");
+			cl_assert_equal_s(path.ptr, check);
+			git__free(check);
+#endif
+
+			cl_git_pass(git_buf_puts(&path, "/testfile"));
+			cl_git_mkfile(path.ptr, "find me");
+
+			cl_git_pass(git_futils_find_global_file(&found, "testfile"));
+
+#ifdef GIT_WIN32
+			/* do another check with HOME unset */
+			cl_git_pass(cl_setenv("HOME", NULL));
+			cl_git_pass(git_futils_find_global_file(&found, "testfile"));
+#endif
+		}
+	}
+
+	git_buf_free(&path);
+	git_buf_free(&found);
+}