read-cache: optionally disallow NTFS .git variants

The point of disallowing ".git" in the index is that we
would never want to accidentally overwrite files in the
repository directory. But this means we need to respect the
filesystem's idea of when two paths are equal. The prior
commit added a helper to make such a comparison for NTFS
and FAT32; let's use it in verify_path().

We make this check optional for two reasons:

  1. It restricts the set of allowable filenames, which is
     unnecessary for people who are not on NTFS nor FAT32.
     In practice this probably doesn't matter, though, as
     the restricted names are rather obscure and almost
     certainly would never come up in practice.

  2. It has a minor performance penalty for every path we
     insert into the index.

This patch ties the check to the core.protectNTFS config
option. Though this is expected to be most useful on Windows,
we allow it to be set everywhere, as NTFS may be mounted on
other platforms. The variable does default to on for Windows,
though.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/config.txt

@@ -239,6 +239,12 @@ core.protectHFS::
 	be considered equivalent to `.git` on an HFS+ filesystem.
 	Defaults to `true` on Mac OS, and `false` elsewhere.
 
+core.protectNTFS::
+	If set to true, do not allow checkout of paths that would
+	cause problems with the NTFS filesystem, e.g. conflict with
+	8.3 "short" names.
+	Defaults to `true` on Windows, and `false` elsewhere.
+
 core.trustctime::
 	If false, the ctime differences between the index and the
 	working tree are ignored; useful when the inode change time

cache.h

@@ -585,6 +585,7 @@ extern int core_preload_index;
 extern int core_apply_sparse_checkout;
 extern int precomposed_unicode;
 extern int protect_hfs;
+extern int protect_ntfs;
 
 /*
  * The character that begins a commented line in user-editable file

config.c

@@ -886,6 +886,11 @@ static int git_default_core_config(const char *var, const char *value)
 		return 0;
 	}
 
+	if (!strcmp(var, "core.protectntfs")) {
+		protect_ntfs = git_config_bool(var, value);
+		return 0;
+	}
+
 	/* Add other config variables here and to Documentation/config.txt. */
 	return 0;
 }

config.mak.uname

@@ -362,6 +362,7 @@ ifeq ($(uname_S),Windows)
 	EXTLIBS = user32.lib advapi32.lib shell32.lib wininet.lib ws2_32.lib
 	PTHREAD_LIBS =
 	lib =
+	BASIC_CFLAGS += -DPROTECT_NTFS_DEFAULT=1
 ifndef DEBUG
 	BASIC_CFLAGS += -GL -Os -MT
 	BASIC_LDFLAGS += -LTCG
@@ -506,6 +507,7 @@ ifneq (,$(findstring MINGW,$(uname_S)))
 	COMPAT_OBJS += compat/mingw.o compat/winansi.o \
 		compat/win32/pthread.o compat/win32/syslog.o \
 		compat/win32/dirent.o
+	BASIC_CFLAGS += -DPROTECT_NTFS_DEFAULT=1
 	BASIC_LDFLAGS += -Wl,--large-address-aware
 	EXTLIBS += -lws2_32
 	GITLIBS += git.res

environment.c

@@ -68,6 +68,11 @@ unsigned long pack_size_limit_cfg;
 #endif
 int protect_hfs = PROTECT_HFS_DEFAULT;
 
+#ifndef PROTECT_NTFS_DEFAULT
+#define PROTECT_NTFS_DEFAULT 0
+#endif
+int protect_ntfs = PROTECT_NTFS_DEFAULT;
+
 /*
  * The character that begins a commented line in user-editable file
  * that is subject to stripspace.

read-cache.c

@@ -789,6 +789,8 @@ int verify_path(const char *path)
 inside:
 			if (protect_hfs && is_hfs_dotgit(path))
 				return 0;
+			if (protect_ntfs && is_ntfs_dotgit(path))
+				return 0;
 			c = *path++;
 			if ((c == '.' && !verify_dotfile(path)) ||
 			    is_dir_sep(c) || c == '\0')

t/t1014-read-tree-confusing.sh

@@ -15,8 +15,17 @@ test_expect_success 'enable core.protectHFS for rejection tests' '
 	git config core.protectHFS true
 '
 
+test_expect_success 'enable core.protectNTFS for rejection tests' '
+	git config core.protectNTFS true
+'
+
 while read path pretty; do
 	: ${pretty:=$path}
+	case "$path" in
+	*SPACE)
+		path="${path%SPACE} "
+		;;
+	esac
 	test_expect_success "reject $pretty at end of path" '
 		printf "100644 blob %s\t%s" "$blob" "$path" >tree &&
 		bogus=$(git mktree <tree) &&
@@ -36,6 +45,10 @@ done <<-EOF
 ${u200c}.Git {u200c}.Git
 .gI${u200c}T .gI{u200c}T
 .GiT${u200c} .GiT{u200c}
+git~1
+.git.SPACE .git.{space}
+.\\\\.GIT\\\\foobar backslashes
+.git\\\\foobar backslashes2
 EOF
 
 test_expect_success 'utf-8 paths allowed with core.protectHFS off' '