Create new terminal sessions with directory of active session

This mimics the behaviour of most tabbed terminal emulators.

Fixes #1009.

Author: fornwall

app/src/main/java/com/termux/app/TermuxActivity.java

@@ -603,7 +603,9 @@ void addNewSession(boolean failSafe, String sessionName) {
             new AlertDialog.Builder(this).setTitle(R.string.max_terminals_reached_title).setMessage(R.string.max_terminals_reached_message)
                 .setPositiveButton(android.R.string.ok, null).show();
         } else {
-            TerminalSession newSession = mTermService.createTermSession(null, null, null, failSafe);
+            TerminalSession currentSession = getCurrentTermSession();
+            String workingDirectory = (currentSession == null) ? null : currentSession.getCwd();
+            TerminalSession newSession = mTermService.createTermSession(null, null, workingDirectory, failSafe);
             if (sessionName != null) {
                 newSession.mSessionName = sessionName;
             }

terminal-emulator/src/main/java/com/termux/terminal/TerminalSession.java

@@ -8,6 +8,7 @@
 import android.system.OsConstants;
 import android.util.Log;
 
+import java.io.File;
 import java.io.FileDescriptor;
 import java.io.FileInputStream;
 import java.io.FileOutputStream;
@@ -339,4 +340,25 @@ public int getPid() {
         return mShellPid;
     }
 
+    /** Returns the shell's working directory or null if it was unavailable. */
+    public String getCwd() {
+        if (mShellPid < 1) {
+            return null;
+        }
+        try {
+            final String cwdSymlink = String.format("/proc/%s/cwd/", mShellPid);
+            String outputPath = new File(cwdSymlink).getCanonicalPath();
+            if (!outputPath.endsWith("/")) {
+                outputPath += '/';
+            }
+            if (!cwdSymlink.equals(outputPath)) {
+                return outputPath;
+            }
+        } catch (IOException | SecurityException e) {
+            Log.e(EmulatorDebug.LOG_TAG, "Error getting current directory", e);
+        }
+        return null;
+    }
+
+
 }