Merge pull request git-for-windows#1897 from piscisaureus/symlink-attr

dscho · dscho · commit 95a1de263958 · 2021-03-27T09:45:57.000+01:00
Specify symlink type in .gitattributes
diff --git a/Documentation/gitattributes.txt b/Documentation/gitattributes.txt
@@ -383,6 +383,36 @@ sign `$` upon checkout.  Any byte sequence that begins with
 with `$Id$` upon check-in.
 
 
+`symlink`
+^^^^^^^^^
+
+On Windows, symbolic links have a type: a "file symlink" must point at
+a file, and a "directory symlink" must point at a directory. If the
+type of symlink does not match its target, it doesn't work.
+
+Git does not record the type of symlink in the index or in a tree. On
+checkout it'll guess the type, which only works if the target exists
+at the time the symlink is created. This may often not be the case,
+for example when the link points at a directory inside a submodule.
+
+The `symlink` attribute allows you to explicitly set the type of symlink
+to `file` or `dir`, so Git doesn't have to guess. If you have a set of
+symlinks that point at other files, you can do:
+
+------------------------
+*.gif 	symlink=file
+------------------------
+
+To tell Git that a symlink points at a directory, use:
+
+------------------------
+tools_folder 	symlink=dir
+------------------------
+
+The `symlink` attribute is ignored on platforms other than Windows,
+since they don't distinguish between different types of symlinks.
+
+
 `filter`
 ^^^^^^^^
 
diff --git a/apply.c b/apply.c
@@ -4358,7 +4358,7 @@ static int try_create_file(struct apply_state *state, const char *path,
 		/* Although buf:size is counted string, it also is NUL
 		 * terminated.
 		 */
-		return !!symlink(buf, path);
+		return !!create_symlink(state && state->repo ? state->repo->index : NULL, buf, path);
 
 	fd = open(path, O_CREAT | O_EXCL | O_WRONLY, (mode & 0100) ? 0777 : 0666);
 	if (fd < 0)
diff --git a/builtin/difftool.c b/builtin/difftool.c
@@ -504,7 +504,7 @@ static int run_dir_diff(const char *extcmd, int symlinks, const char *prefix,
 				}
 				add_path(&wtdir, wtdir_len, dst_path);
 				if (symlinks) {
-					if (symlink(wtdir.buf, rdir.buf)) {
+					if (create_symlink(lstate.istate, wtdir.buf, rdir.buf)) {
 						ret = error_errno("could not symlink '%s' to '%s'", wtdir.buf, rdir.buf);
 						goto finish;
 					}
diff --git a/builtin/init-db.c b/builtin/init-db.c
@@ -79,7 +79,7 @@ static void copy_templates_1(struct strbuf *path, struct strbuf *template_path,
 			if (strbuf_readlink(&lnk, template_path->buf,
 					    st_template.st_size) < 0)
 				die_errno(_("cannot readlink '%s'"), template_path->buf);
-			if (symlink(lnk.buf, path->buf))
+			if (create_symlink(NULL, lnk.buf, path->buf))
 				die_errno(_("cannot symlink '%s' '%s'"),
 					  lnk.buf, path->buf);
 			strbuf_release(&lnk);
@@ -313,7 +313,7 @@ static int create_default_files(const char *template_path,
 		path = git_path_buf(&buf, "tXXXXXX");
 		if (!close(xmkstemp(path)) &&
 		    !unlink(path) &&
-		    !symlink("testing", path) &&
+		    !create_symlink(NULL, "testing", path) &&
 		    !lstat(path, &st1) &&
 		    S_ISLNK(st1.st_mode))
 			unlink(path); /* good */
diff --git a/compat/mingw.c b/compat/mingw.c
@@ -10,6 +10,7 @@
 #include "../config.h"
 #include "dir.h"
 #include "win32/fscache.h"
+#include "../attr.h"
 
 #define HCAST(type, handle) ((type)(intptr_t)handle)
 
@@ -425,6 +426,54 @@ static void process_phantom_symlinks(void)
 	LeaveCriticalSection(&phantom_symlinks_cs);
 }
 
+static int create_phantom_symlink(wchar_t *wtarget, wchar_t *wlink)
+{
+	int len;
+
+	/* create file symlink */
+	if (!CreateSymbolicLinkW(wlink, wtarget, symlink_file_flags)) {
+		errno = err_win_to_posix(GetLastError());
+		return -1;
+	}
+
+	/* convert to directory symlink if target exists */
+	switch (process_phantom_symlink(wtarget, wlink)) {
+	case PHANTOM_SYMLINK_RETRY: {
+		/* if target doesn't exist, add to phantom symlinks list */
+		wchar_t wfullpath[MAX_LONG_PATH];
+		struct phantom_symlink_info *psi;
+
+		/* convert to absolute path to be independent of cwd */
+		len = GetFullPathNameW(wlink, MAX_LONG_PATH, wfullpath, NULL);
+		if (!len || len >= MAX_LONG_PATH) {
+			errno = err_win_to_posix(GetLastError());
+			return -1;
+		}
+
+		/* over-allocate and fill phantom_symlink_info structure */
+		psi = xmalloc(sizeof(struct phantom_symlink_info) +
+			      sizeof(wchar_t) * (len + wcslen(wtarget) + 2));
+		psi->wlink = (wchar_t *)(psi + 1);
+		wcscpy(psi->wlink, wfullpath);
+		psi->wtarget = psi->wlink + len + 1;
+		wcscpy(psi->wtarget, wtarget);
+
+		EnterCriticalSection(&phantom_symlinks_cs);
+		psi->next = phantom_symlinks;
+		phantom_symlinks = psi;
+		LeaveCriticalSection(&phantom_symlinks_cs);
+		break;
+	}
+	case PHANTOM_SYMLINK_DIRECTORY:
+		/* if we created a dir symlink, process other phantom symlinks */
+		process_phantom_symlinks();
+		break;
+	default:
+		break;
+	}
+	return 0;
+}
+
 /* Normalizes NT paths as returned by some low-level APIs. */
 static wchar_t *normalize_ntpath(wchar_t *wbuf)
 {
@@ -2770,7 +2819,38 @@ int link(const char *oldpath, const char *newpath)
 	return 0;
 }
 
-int symlink(const char *target, const char *link)
+enum symlink_type {
+	SYMLINK_TYPE_UNSPECIFIED = 0,
+	SYMLINK_TYPE_FILE,
+	SYMLINK_TYPE_DIRECTORY,
+};
+
+static enum symlink_type check_symlink_attr(struct index_state *index, const char *link)
+{
+	static struct attr_check *check;
+	const char *value;
+
+	if (!index)
+		return SYMLINK_TYPE_UNSPECIFIED;
+
+	if (!check)
+		check = attr_check_initl("symlink", NULL);
+
+	git_check_attr(index, link, check);
+
+	value = check->items[0].value;
+	if (ATTR_UNSET(value))
+		return SYMLINK_TYPE_UNSPECIFIED;
+	if (!strcmp(value, "file"))
+		return SYMLINK_TYPE_FILE;
+	if (!strcmp(value, "dir") || !strcmp(value, "directory"))
+		return SYMLINK_TYPE_DIRECTORY;
+
+	warning(_("ignoring invalid symlink type '%s' for '%s'"), value, link);
+	return SYMLINK_TYPE_UNSPECIFIED;
+}
+
+int mingw_create_symlink(struct index_state *index, const char *target, const char *link)
 {
 	wchar_t wtarget[MAX_LONG_PATH], wlink[MAX_LONG_PATH];
 	int len;
@@ -2790,48 +2870,31 @@ int symlink(const char *target, const char *link)
 		if (wtarget[len] == '/')
 			wtarget[len] = '\\';
 
-	/* create file symlink */
-	if (!CreateSymbolicLinkW(wlink, wtarget, symlink_file_flags)) {
-		errno = err_win_to_posix(GetLastError());
-		return -1;
-	}
-
-	/* convert to directory symlink if target exists */
-	switch (process_phantom_symlink(wtarget, wlink)) {
-	case PHANTOM_SYMLINK_RETRY:	{
-		/* if target doesn't exist, add to phantom symlinks list */
-		wchar_t wfullpath[MAX_LONG_PATH];
-		struct phantom_symlink_info *psi;
-
-		/* convert to absolute path to be independent of cwd */
-		len = GetFullPathNameW(wlink, MAX_LONG_PATH, wfullpath, NULL);
-		if (!len || len >= MAX_LONG_PATH) {
-			errno = err_win_to_posix(GetLastError());
-			return -1;
-		}
-
-		/* over-allocate and fill phantom_symlink_info structure */
-		psi = xmalloc(sizeof(struct phantom_symlink_info)
-			+ sizeof(wchar_t) * (len + wcslen(wtarget) + 2));
-		psi->wlink = (wchar_t *)(psi + 1);
-		wcscpy(psi->wlink, wfullpath);
-		psi->wtarget = psi->wlink + len + 1;
-		wcscpy(psi->wtarget, wtarget);
-
-		EnterCriticalSection(&phantom_symlinks_cs);
-		psi->next = phantom_symlinks;
-		phantom_symlinks = psi;
-		LeaveCriticalSection(&phantom_symlinks_cs);
-		break;
-	}
-	case PHANTOM_SYMLINK_DIRECTORY:
-		/* if we created a dir symlink, process other phantom symlinks */
+	switch (check_symlink_attr(index, link)) {
+	case SYMLINK_TYPE_UNSPECIFIED:
+		/* Create a phantom symlink: it is initially created as a file
+		 * symlink, but may change to a directory symlink later if/when
+		 * the target exists. */
+		return create_phantom_symlink(wtarget, wlink);
+	case SYMLINK_TYPE_FILE:
+		if (!CreateSymbolicLinkW(wlink, wtarget, symlink_file_flags))
+			break;
+		return 0;
+	case SYMLINK_TYPE_DIRECTORY:
+		if (!CreateSymbolicLinkW(wlink, wtarget,
+					 symlink_directory_flags))
+			break;
+		/* There may be dangling phantom symlinks that point at this
+		 * one, which should now morph into directory symlinks. */
 		process_phantom_symlinks();
-		break;
+		return 0;
 	default:
-		break;
+		BUG("unhandled symlink type");
 	}
-	return 0;
+
+	/* CreateSymbolicLinkW failed. */
+	errno = err_win_to_posix(GetLastError());
+	return -1;
 }
 
 #ifndef _WINNT_H
diff --git a/compat/mingw.h b/compat/mingw.h
@@ -213,8 +213,10 @@ int setitimer(int type, struct itimerval *in, struct itimerval *out);
 int sigaction(int sig, struct sigaction *in, struct sigaction *out);
 int link(const char *oldpath, const char *newpath);
 int uname(struct utsname *buf);
-int symlink(const char *target, const char *link);
 int readlink(const char *path, char *buf, size_t bufsiz);
+struct index_state;
+int mingw_create_symlink(struct index_state *index, const char *target, const char *link);
+#define create_symlink mingw_create_symlink
 
 /*
  * replacements of existing functions
diff --git a/entry.c b/entry.c
@@ -291,7 +291,7 @@ static int write_entry(struct cache_entry *ce,
 		if (!has_symlinks || to_tempfile)
 			goto write_file_entry;
 
-		ret = symlink(new_blob, path);
+		ret = create_symlink(state->istate, new_blob, path);
 		free(new_blob);
 		if (ret)
 			return error_errno("unable to create symlink %s", path);
diff --git a/git-compat-util.h b/git-compat-util.h
@@ -412,6 +412,15 @@ static inline int git_has_dir_sep(const char *path)
 #define is_mount_point is_mount_point_via_stat
 #endif
 
+#ifndef create_symlink
+struct index_state;
+static inline int git_create_symlink(struct index_state *index, const char *target, const char *link)
+{
+	return symlink(target, link);
+}
+#define create_symlink git_create_symlink
+#endif
+
 #ifndef query_user_email
 #define query_user_email() NULL
 #endif
diff --git a/merge-recursive.c b/merge-recursive.c
@@ -986,7 +986,7 @@ static int update_file_flags(struct merge_options *opt,
 			char *lnk = xmemdupz(buf, size);
 			safe_create_leading_directories_const(path);
 			unlink(path);
-			if (symlink(lnk, path))
+			if (create_symlink(&opt->priv->orig_index, lnk, path))
 				ret = err(opt, _("failed to symlink '%s': %s"),
 					  path, strerror(errno));
 			free(lnk);
diff --git a/refs/files-backend.c b/refs/files-backend.c
@@ -1788,7 +1788,7 @@ static int create_ref_symlink(struct ref_lock *lock, const char *target)
 #ifndef NO_SYMLINK_HEAD
 	char *ref_path = get_locked_file_path(&lock->lk);
 	unlink(ref_path);
-	ret = symlink(target, ref_path);
+	ret = create_symlink(NULL, target, ref_path);
 	free(ref_path);
 
 	if (ret)
diff --git a/t/t2040-checkout-symlink-attr.sh b/t/t2040-checkout-symlink-attr.sh
@@ -0,0 +1,46 @@
+#!/bin/sh
+
+test_description='checkout symlinks with `symlink` attribute on Windows
+
+Ensures that Git for Windows creates symlinks of the right type,
+as specified by the `symlink` attribute in `.gitattributes`.'
+
+# Tell MSYS to create native symlinks. Without this flag test-lib's
+# prerequisite detection for SYMLINKS doesn't detect the right thing.
+MSYS=winsymlinks:nativestrict && export MSYS
+
+. ./test-lib.sh
+
+if ! test_have_prereq MINGW,SYMLINKS
+then
+	skip_all='skipping $0: MinGW-only test, which requires symlink support.'
+	test_done
+fi
+
+# Adds a symlink to the index without clobbering the work tree.
+cache_symlink () {
+	sha=$(printf '%s' "$1" | git hash-object --stdin -w) &&
+	git update-index --add --cacheinfo 120000,$sha,"$2"
+}
+
+test_expect_success 'checkout symlinks with attr' '
+	cache_symlink file1 file-link &&
+	cache_symlink dir dir-link &&
+
+	printf "file-link symlink=file\ndir-link symlink=dir\n" >.gitattributes &&
+	git add .gitattributes &&
+
+	git checkout . &&
+
+	mkdir dir &&
+	echo "[a]b=c" >file1 &&
+	echo "[x]y=z" >dir/file2 &&
+
+	# MSYS2 is very forgiving, it will resolve symlinks even if the
+	# symlink type is incorrect. To make this test meaningful, try
+	# them with a native, non-MSYS executable, such as `git config`.
+	test "$(git config -f file-link a.b)" = "c" &&
+	test "$(git config -f dir-link/file2 x.y)" = "z"
+'
+
+test_done

Original file line number	Diff line number	Diff line change
`@@ -504,7 +504,7 @@ static int run_dir_diff(const char extcmd, int symlinks, const char prefix,`
`504`	`504`	`}`
`505`	`505`	`add_path(&wtdir, wtdir_len, dst_path);`
`506`	`506`	`if (symlinks) {`
`507`		`- if (symlink(wtdir.buf, rdir.buf)) {`
	`507`	`+ if (create_symlink(lstate.istate, wtdir.buf, rdir.buf)) {`
`508`	`508`	`ret = error_errno("could not symlink '%s' to '%s'", wtdir.buf, rdir.buf);`
`509`	`509`	`goto finish;`
`510`	`510`	`}`