Bash integration: Fix clone-in-kitty not working on bash >= 5.2 if environment variable values contain newlines or other special characters

Bash >= 5.2 changed the export command to output values using $' escaping when they contain special characters.
Fixes #5629

kitty/bash.py

@@ -0,0 +1,138 @@
+#!/usr/bin/env python
+# License: GPLv3 Copyright: 2022, Kovid Goyal <kovid at kovidgoyal.net>
+
+import string
+from typing import Dict, List, Tuple
+
+ansi_c_escapes = {
+    'a': '\a',
+    'b': '\b',
+    'e': '\x1b',
+    'E': '\x1b',
+    'f': '\f',
+    'n': '\n',
+    'r': '\r',
+    't': '\t',
+    'v': '\v',
+    '\\': '\\',
+    "'": "'",
+    '"': '"',
+    '?': '?',
+}
+
+
+def ctrl_mask_char(ch: str) -> str:
+    try:
+        o = ord(ch)
+    except Exception:
+        return ch
+    if o > 127:
+        return ch
+    return chr(o & 0b0011111)
+
+
+def read_digit(text: str, pos: int, max_len: int, valid_digits: str, base: int) -> Tuple[str, int]:
+    epos = pos
+    while (epos - pos) <= max_len and epos < len(text) and text[epos] in valid_digits:
+        epos += 1
+    raw = text[pos:epos]
+    try:
+        return chr(int(raw, base)), epos
+    except Exception:
+        return raw, epos
+
+
+def read_hex_digit(text: str, pos: int, max_len: int) -> Tuple[str, int]:
+    return read_digit(text, pos, max_len, string.digits + 'abcdefABCDEF', 16)
+
+
+def read_octal_digit(text: str, pos: int) -> Tuple[str, int]:
+    return read_digit(text, pos, 3, '01234567', 8)
+
+
+def decode_ansi_c_quoted_string(text: str, pos: int) -> Tuple[str, int]:
+    buf: List[str] = []
+    a = buf.append
+    while pos < len(text):
+        ch = text[pos]
+        pos += 1
+        if ch == '\\':
+            ec = text[pos]
+            pos += 1
+            ev = ansi_c_escapes.get(ec)
+            if ev is None:
+                if ec == 'c' and pos + 1 < len(text):
+                    a(ctrl_mask_char(text[pos]))
+                    pos += 1
+                elif ec in 'xuU' and pos + 1 < len(text):
+                    hd, pos = read_hex_digit(text, pos, {'x': 2, 'u': 4, 'U': 8}[ec])
+                    a(hd)
+                elif ec.isdigit():
+                    hd, pos = read_octal_digit(text, pos-1)
+                    a(hd)
+                else:
+                    a(ec)
+            else:
+                a(ev)
+        elif ch == "'":
+            break
+        else:
+            a(ch)
+    return ''.join(buf), pos
+
+
+def decode_double_quoted_string(text: str, pos: int) -> Tuple[str, int]:
+    escapes = r'"\$`'
+    buf: List[str] = []
+    a = buf.append
+    while pos < len(text):
+        ch = text[pos]
+        pos += 1
+        if ch == '\\':
+            if text[pos] in escapes:
+                a(text[pos])
+                pos += 1
+                continue
+            a(ch)
+        elif ch == '"':
+            break
+        else:
+            a(ch)
+    return ''.join(buf), pos
+
+
+def parse_modern_bash_env(text: str) -> Dict[str, str]:
+    ans = {}
+    for line in text.splitlines():
+        idx = line.find('=')
+        if idx < 0:
+            break
+        key = line[:idx].rpartition(' ')[2]
+        val = line[idx+1:]
+        if val.startswith('"'):
+            val = decode_double_quoted_string(val, 1)[0]
+        else:
+            val = decode_ansi_c_quoted_string(val, 2)[0]
+        ans[key] = val
+    return ans
+
+
+def parse_bash_env(text: str, bash_version: str) -> Dict[str, str]:
+    # See https://www.gnu.org/software/bash/manual/html_node/Double-Quotes.html
+    parts = bash_version.split('.')
+    bv = tuple(map(int, parts[:2]))
+    if bv >= (5, 2):
+        return parse_modern_bash_env(text)
+    ans = {}
+    pos = 0
+    while pos < len(text):
+        idx = text.find('="', pos)
+        if idx < 0:
+            break
+        i = text.rfind(' ', 0, idx)
+        if i < 0:
+            break
+        key = text[i+1:idx]
+        pos = idx + 2
+        ans[key], pos = decode_double_quoted_string(text, pos)
+    return ans