don't cache environment variables, fix non-ASCII environment variables

GitCheetah caches environment variables when spawning the first child
process. Thus, updates to the hosting explorer process's environment are
not reflected in subsequently spawned child processes.

Note: if and when explorer updates its environment variables from the
registry seems to depend on the Windows version.

Additionally, non-ASCII environment variables are mangled in child
processes, as GetEnvironmentStringsA returns OEM-encoded strings, but
CreateProcessA expects ANSI.

Remove the copying / caching of the entire environment. When spawning
child processes, just tweak the PATH variable temporarily.

Reading a single environment variable (GetEnvironmentVariableA) instead of
the entire environment (GetEnvironmentStringsA) implicitly fixes non-ASCII
variables.

Signed-off-by: Karsten Blees <blees@dcon.de>

explorer/systeminfo.c

@@ -101,71 +101,37 @@ int is_directory(const char *path)
 	return (FILE_ATTRIBUTE_DIRECTORY & GetFileAttributes(path));
 }
 
-/*
- * builds an array of environment variables,
- * as expected by mingw_spawnvpe
- */
-static char **env_for_git()
+pid_t fork_process(const char *cmd, const char **args, const char *wd)
 {
-	static char **environment;
-
-	/*
-	 * if we can't find path to msys in the registry, return NULL and
-	 * the CreateProcess will copy the environment for us
-	 */
-	if (!environment && git_path()) {
-		char *old = GetEnvironmentStrings();
-		size_t space = 0, path_index = -1, name_len = 0;
-		int total = 0, i;
-
-		while (old[space]) {
-			/* if it's PATH variable (could be Path= too!) */
-			if (!strnicmp(old + space, "PATH=", 5)) {
-				path_index = space;
-				name_len = 5;
-			}
-
-			while (old[space])
-				space++;
-			space++; /* skip var-terminating NULL */
-
-			total++;
-		}
-
-		if (path_index == -1)
-			path_index = space;
-
-		environment = malloc(sizeof(*environment) * (total + 1));
-		space = 0;
-		for (i = 0; i < total; i++) {
-			if (path_index == space) {
-				char *path = old + space + name_len;
-				size_t len;
-				environment[i] = malloc(strlen(path) + 1 +
-					2 * strlen(git_path()) + 32);
-				len = sprintf(environment[i],
-					"PATH=%s%s%s", git_path(),
-					*path ? ";" : "", path);
-			} else
-				environment[i] = strdup(old + space);
-
-			while (old[space])
-				space++;
-			space++; /* skip var-terminating NULL */
+	pid_t result;
+	char *oldpath = NULL;
+	const char *gitpath = git_path();
+
+	/* if gitpath is set, temporarily set PATH=<gitpath>;%PATH% */
+	if (gitpath) {
+		int len;
+		struct strbuf path = STRBUF_INIT;
+		strbuf_addstr(&path, gitpath);
+		len = GetEnvironmentVariable("PATH", NULL, 0);
+		if (len) {
+			oldpath = malloc(len);
+			GetEnvironmentVariable("PATH", oldpath, len);
+			strbuf_addch(&path, ';');
+			strbuf_addstr(&path, oldpath);
 		}
-
-		/* mark the end of the array */
-		environment[i] = 0;
-
-		FreeEnvironmentStrings(old);
+		SetEnvironmentVariable("PATH", path.buf);
+		strbuf_release(&path);
 	}
 
-	return environment;
-}
+	/* spawn child process */
+	result = mingw_spawnvpe_cwd(cmd, args, NULL, wd);
 
-pid_t fork_process(const char *cmd, const char **args, const char *wd)
-{
-	return mingw_spawnvpe_cwd(cmd, args, env_for_git(), wd);
+	/* reset PATH to previous value */
+	if (gitpath) {
+		SetEnvironmentVariable("PATH", oldpath);
+		free(oldpath);
+	}
+	return result;
 }
 
 int wait_for_process(pid_t pid, int max_time, int *errcode)