checkout: disallow bad paths on win32

Disallow:
 1. paths with trailing dot
 2. paths with trailing space
 3. paths with trailing colon
 4. paths that are 8.3 short names of .git folders ("GIT~1")
 5. paths that are reserved path names (COM1, LPT1, etc).
 6. paths with reserved DOS characters (colons, asterisks, etc)

These paths would (without \\?\ syntax) be elided to other paths - for
example, ".git." would be written as ".git".  As a result, writing these
paths literally (using \\?\ syntax) makes them hard to operate with from
the shell, Windows Explorer or other tools.  Disallow these.

2 files changed, 51 insertions, 0 deletions

diff --git a/src/win32/path_w32.c b/src/win32/path_w32.c
index f0eacaa63..d66969c4d 100644
--- a/src/win32/path_w32.c
+++ b/src/win32/path_w32.c
@@ -267,3 +267,39 @@ int git_win32_path_to_utf8(git_win32_utf8_path dest, const wchar_t *src)
 
 	return len;
 }
+
+char *git_win32_path_8dot3_name(const char *path)
+{
+	git_win32_path longpath, shortpath;
+	wchar_t *start;
+	char *shortname;
+	int len, namelen = 1;
+
+	if (git_win32_path_from_utf8(longpath, path) < 0)
+		return NULL;
+
+	len = GetShortPathNameW(longpath, shortpath, GIT_WIN_PATH_UTF16);
+
+	while (len && shortpath[len-1] == L'\\')
+		shortpath[--len] = L'\0';
+
+	if (len == 0 || len >= GIT_WIN_PATH_UTF16)
+		return NULL;
+
+	for (start = shortpath + (len - 1);
+		start > shortpath && *(start-1) != '/' && *(start-1) != '\\';
+		start--)
+		namelen++;
+
+	/* We may not have actually been given a short name.  But if we have,
+	 * it will be in the ASCII byte range, so we don't need to worry about
+	 * multi-byte sequences and can allocate naively.
+	 */
+	if (namelen > 12 || (shortname = git__malloc(namelen + 1)) == NULL)
+		return NULL;
+
+	if ((len = git__utf16_to_8(shortname, namelen + 1, start)) < 0)
+		return NULL;
+
+	return shortname;
+}
diff --git a/src/win32/path_w32.h b/src/win32/path_w32.h
index dc7a68e59..1d10166e8 100644
--- a/src/win32/path_w32.h
+++ b/src/win32/path_w32.h
@@ -26,6 +26,11 @@
  */
 #define GIT_WIN_PATH_UTF8		(259 * 3 + 1)
 
+/*
+ * The length of a Windows "shortname", for 8.3 compatibility.
+ */
+#define GIT_WIN_PATH_SHORTNAME  13
+
 /* Win32 path types */
 typedef wchar_t git_win32_path[GIT_WIN_PATH_UTF16];
 typedef char git_win32_utf8_path[GIT_WIN_PATH_UTF8];
@@ -62,4 +67,14 @@ extern int git_win32_path_canonicalize(git_win32_path path);
  */
 extern int git_win32_path_to_utf8(git_win32_utf8_path dest, const wchar_t *src);
 
+/**
+ * Get the short name for the terminal path component in the given path.
+ * For example, given "C:\Foo\Bar\Asdf.txt", this will return the short name
+ * for the file "Asdf.txt".
+ *
+ * @param path The given path in UTF-8
+ * @return The name of the shortname for the given path
+ */
+extern char *git_win32_path_8dot3_name(const char *path);
+
 #endif