From 8eac1f947715c47f877e577515a3289aba705513 Mon Sep 17 00:00:00 2001
From: Jilles Tjoelker <jilles@FreeBSD.org>
Date: Sat, 17 Apr 2010 14:35:46 +0000
Subject: [PATCH] sh: On startup of the shell, use PWD from the environment if
 it is valid. Unset PWD if it is incorrect and no value for it can be
 determined. This preserves the logical current directory across shell
 invocations.

Example (assuming /home is a symlink):
$ cd
$ pwd
/home/foo
$ sh
$ pwd
/home/foo

Formerly the second pwd would show the physical path (symlinks resolved).
---
 bin/sh/cd.c                               | 27 ++++++++++++++++++-----
 bin/sh/cd.h                               |  2 +-
 bin/sh/main.c                             |  5 +----
 tools/regression/bin/sh/parameters/pwd2.0 | 24 ++++++++++++++++++++
 4 files changed, 48 insertions(+), 10 deletions(-)
 create mode 100644 tools/regression/bin/sh/parameters/pwd2.0

diff --git a/bin/sh/cd.c b/bin/sh/cd.c
index 40801ba2c97f..aee06e8fb000 100644
--- a/bin/sh/cd.c
+++ b/bin/sh/cd.c
@@ -70,6 +70,7 @@ STATIC int docd(char *, int, int);
 STATIC char *getcomponent(void);
 STATIC char *findcwd(char *);
 STATIC void updatepwd(char *);
+STATIC char *getpwd(void);
 STATIC char *getpwd2(void);
 
 STATIC char *curdir = NULL;	/* current working directory */
@@ -351,7 +352,7 @@ pwdcmd(int argc, char **argv)
 /*
  * Get the current directory and cache the result in curdir.
  */
-char *
+STATIC char *
 getpwd(void)
 {
 	char *p;
@@ -374,7 +375,6 @@ getpwd(void)
 STATIC char *
 getpwd2(void)
 {
-	struct stat stdot, stpwd;
 	char *pwd;
 	int i;
 
@@ -387,12 +387,29 @@ getpwd2(void)
 			break;
 	}
 
-	pwd = getenv("PWD");
+	return NULL;
+}
+
+/*
+ * Initialize PWD in a new shell.
+ * If the shell is interactive, we need to warn if this fails.
+ */
+void
+pwd_init(int warn)
+{
+	char *pwd;
+	struct stat stdot, stpwd;
+
+	pwd = lookupvar("PWD");
 	if (pwd && *pwd == '/' && stat(".", &stdot) != -1 &&
 	    stat(pwd, &stpwd) != -1 &&
 	    stdot.st_dev == stpwd.st_dev &&
 	    stdot.st_ino == stpwd.st_ino) {
-		return pwd;
+		if (curdir)
+			ckfree(curdir);
+		curdir = savestr(pwd);
 	}
-	return NULL;
+	if (getpwd() == NULL && warn)
+		out2fmt_flush("sh: cannot determine working directory\n");
+	setvar("PWD", curdir, VEXPORT);
 }
diff --git a/bin/sh/cd.h b/bin/sh/cd.h
index 0a2d48999e7b..f88ce26ad4c6 100644
--- a/bin/sh/cd.h
+++ b/bin/sh/cd.h
@@ -29,6 +29,6 @@
  * $FreeBSD$
  */
 
-char	*getpwd(void);
+void	 pwd_init(int);
 int	 cdcmd (int, char **);
 int	 pwdcmd(int, char **);
diff --git a/bin/sh/main.c b/bin/sh/main.c
index 50a88132ab37..ecbb12dc6401 100644
--- a/bin/sh/main.c
+++ b/bin/sh/main.c
@@ -153,10 +153,7 @@ main(int argc, char *argv[])
 	init();
 	setstackmark(&smark);
 	procargs(argc, argv);
-	if (getpwd() == NULL && iflag)
-		out2fmt_flush("sh: cannot determine working directory\n");
-	if (getpwd() != NULL)
-		setvar ("PWD", getpwd(), VEXPORT);
+	pwd_init(iflag);
 	if (iflag)
 		chkmail(1);
 	if (argv[0] && argv[0][0] == '-') {
diff --git a/tools/regression/bin/sh/parameters/pwd2.0 b/tools/regression/bin/sh/parameters/pwd2.0
new file mode 100644
index 000000000000..29b5531aaa85
--- /dev/null
+++ b/tools/regression/bin/sh/parameters/pwd2.0
@@ -0,0 +1,24 @@
+# $FreeBSD$
+# Check that PWD is exported and accepted from the environment.
+set -e
+
+T=$(mktemp -d ${TMPDIR:-/tmp}/sh-test.XXXXXX)
+trap 'rm -rf $T' 0
+cd -P $T
+TP=$(pwd)
+mkdir test1
+ln -s test1 link
+cd link
+[ "$PWD" = "$TP/link" ]
+[ "$(pwd)" = "$TP/link" ]
+[ "$(pwd -P)" = "$TP/test1" ]
+[ "$(sh -c pwd)" = "$TP/link" ]
+[ "$(sh -c pwd\ -P)" = "$TP/test1" ]
+cd ..
+[ "$(pwd)" = "$TP" ]
+cd -P link
+[ "$PWD" = "$TP/test1" ]
+[ "$(pwd)" = "$TP/test1" ]
+[ "$(pwd -P)" = "$TP/test1" ]
+[ "$(sh -c pwd)" = "$TP/test1" ]
+[ "$(sh -c pwd\ -P)" = "$TP/test1" ]