fix: escape curly braces for the prompt cwd (#4511)

If a directory was named for example '{RED}', that would get
interpreted as a color string and the prompt would not show the
direcotry name and would color it instead. Using dir names like
'{{foo}}' or simply '{' would break the prompt outright.

There was not much documentation on the prompt formating, but it seems
that escaping a curly by doubling it makes the prompt display all
curlies correctly.

fixes #4381

news/pwd-curly-escape.rst

@@ -0,0 +1,23 @@
+**Added:**
+
+* <news item>
+
+**Changed:**
+
+* Curly braces { } in directory names are now escaped in the prompt
+
+**Deprecated:**
+
+* <news item>
+
+**Removed:**
+
+* <news item>
+
+**Fixed:**
+
+* <news item>
+
+**Security:**
+
+* <news item>

tests/prompt/test_cwd.py

@@ -0,0 +1,16 @@
+from xonsh.prompt.cwd import _replace_home_cwd
+from xonsh.built_ins import XSH
+
+
+def test_cwd_escapes_curly_brackets_with_more_curly_brackets():
+    XSH.env["PWD"] = "{foo}"
+    assert _replace_home_cwd() == "{{foo}}"
+
+    XSH.env["PWD"] = "{{foo}}"
+    assert _replace_home_cwd() == "{{{{foo}}}}"
+
+    XSH.env["PWD"] = "{"
+    assert _replace_home_cwd() == "{{"
+
+    XSH.env["PWD"] = "}}"
+    assert _replace_home_cwd() == "}}}}"

xonsh/prompt/cwd.py

@@ -27,7 +27,8 @@ def _replace_home(x):
 
 
 def _replace_home_cwd():
-    return _replace_home(XSH.env["PWD"])
+    pwd = XSH.env["PWD"].replace("{", "{{").replace("}", "}}")
+    return _replace_home(pwd)
 
 
 def _collapsed_pwd():