copy helper functions from sage-env to sage; backup env to DOT_SAGE

src/bin/sage

@@ -234,6 +234,105 @@ usage_advanced() {
     exit 0
 }
 
+# Resolve all symbolic links in a filename.  This more or less behaves
+# like "readlink -f" except that it does not convert the filename to an
+# absolute path (a relative path remains relative), nor does it treat
+# "." or ".." specially.
+#
+# AUTHOR: Jeroen Demeyer (2011-08-23): Trac tickets #5852 and #11704
+#
+resolvelinks() {
+    # $in is what still needs to be converted (normally has no starting slash)
+    in="$1"
+    # $out is the part which is converted (normally ends with trailing slash)
+    out="./"
+
+    # Move stuff from $in to $out
+    while [ -n "$in" ]; do
+        # Normalize $in by replacing consecutive slashes by one slash
+        while { in_single_slash=${in//\/\//\/}; [ "$in" != "$in_single_slash" ]; }; do
+            in=$in_single_slash
+        done
+
+        # If $in starts with a slash, remove it and set $out to the root
+        in_without_slash=${in/#\//}
+        if [ "$in" != "$in_without_slash" ]; then
+            in=$in_without_slash
+            out="/"
+            continue
+        fi
+
+        # Check that the directory $out exists by trying to cd to it.
+        # If this fails, then cd will show an error message (unlike
+        # test -d "$out"), so no need to be more verbose.
+        ( cd "$out" ) || return $?
+
+
+        # Get the first component of $in
+        f=${in%%/*}
+
+        # If it is not a symbolic link, simply move it to $out
+        if [ ! -L "$out$f" ]; then
+            in=${in#"$f"}
+            out="$out$f"
+
+            # If the new $in starts with a slash, move it to $out
+            in_without_slash=${in/#\//}
+            if [ "$in" != "$in_without_slash" ]; then
+                in=$in_without_slash
+                out="$out/"
+            fi
+            continue
+        fi
+
+        # Now resolve the symbolic link "$f"
+        f_resolved=`readlink -n "$out$f" 2>/dev/null`
+        status=$?
+        # status 127 means readlink could not be found.
+        if [ $status -eq 127 ]; then
+            # We don't have "readlink", try a stupid "ls" hack instead.
+            # This will fail if we have filenames like "a -> b".
+            fls=`ls -l "$out$f" 2>/dev/null`
+            status=$?
+            f_resolved=${fls##*-> }
+
+            # If $fls equals $f_resolved, then certainly
+            # something is wrong
+            if [ $status -eq 0 -a "$fls" = "$f_resolved" ]; then
+                echo >&2 "Cannot parse output from ls -l '$out$f'"
+                return 1
+            fi
+        fi
+        if [ $status -ne 0 ]; then
+            echo >&2 "Cannot read symbolic link '$out$f'"
+            return $status
+        fi
+
+        # In $in, replace $f by $f_resolved (leave $out alone)
+        in=${in/#"$f"/"$f_resolved"}
+    done
+
+    # Return $out
+    echo "$out"
+}
+
+if [ "$DOT_SAGE" = "" ]; then
+    # It is *not* an error if this directory does not exist, it will
+    # be created in src/bin/sage or src/sage/misc/misc.py.
+    # This also works if $HOME/.sage is a symbolic link to a
+    # non-existing directory.
+    DOT_SAGE=`resolvelinks "$HOME/.sage"`
+
+    # In theory, DOT_SAGE is not required to have a trailing slash.
+    # But since there are some issues (#11924, maybe #12221),
+    # we add a slash for safety.
+    DOT_SAGE="${DOT_SAGE}/"
+    mkdir -p "$DOT_SAGE"
+fi
+
+# Back up environment
+/usr/bin/env >"$DOT_SAGE"/orig-env
+
 # Check for '--nodotsage' before sourcing sage-env; otherwise sage-env
 # will already have set some environment variables with the old
 # setting for DOT_SAGE.