Implement shell globbing, tilde expansion, and brace expansion (issues #13, #18)

Unquoted tokens are now expanded through a tilde → brace → glob pipeline
in parse_argv. Quoted tokens (single, double, or backslash) suppress all
expansion. Uses glob(3) with GLOB_NOCHECK for wildcard matching and manual
implementations for tilde (~→$HOME) and brace ({a,b,c}) expansion.

testes/lush/globbing.lua

@@ -0,0 +1,135 @@
+-- testes/lush/globbing.lua
+-- Tests for shell globbing (#13) and tilde expansion (#18).
+
+print "testing globbing and tilde expansion"
+
+-- === wildcard expansion ===
+
+-- *.lua should expand to matching files (we know lush test files exist)
+do
+  local r = `echo *.c`
+  local out = r.stdout:gsub("\n$", "")
+  -- should NOT be the literal "*.c" since .c files exist in the project
+  assert(out ~= "*.c", "expected *.c to expand, got literal: " .. out)
+  assert(out:find("lcmd.c"), "expected lcmd.c in expansion, got: " .. out)
+end
+
+-- no match: keeps literal pattern (GLOB_NOCHECK)
+do
+  local r = `echo *.nonexistent_xyz_9876`
+  local out = r.stdout:gsub("\n$", "")
+  assert(out == "*.nonexistent_xyz_9876",
+         "expected literal, got: " .. out)
+end
+
+-- ? single-char wildcard
+do
+  -- create temp files to test ? pattern
+  os.execute("mkdir -p /tmp/_lush_glob_test")
+  os.execute("touch /tmp/_lush_glob_test/a1 /tmp/_lush_glob_test/b2")
+  local r = `echo /tmp/_lush_glob_test/?1`
+  local out = r.stdout:gsub("\n$", "")
+  assert(out == "/tmp/_lush_glob_test/a1",
+         "expected ?1 match, got: " .. out)
+  os.execute("rm -rf /tmp/_lush_glob_test")
+end
+
+
+-- === quoting suppresses expansion ===
+
+-- double-quoted glob stays literal
+do
+  local r = `echo "*.c"`
+  local out = r.stdout:gsub("\n$", "")
+  assert(out == "*.c", "double-quoted glob expanded: " .. out)
+end
+
+-- single-quoted glob stays literal
+do
+  local r = `echo '*.c'`
+  local out = r.stdout:gsub("\n$", "")
+  assert(out == "*.c", "single-quoted glob expanded: " .. out)
+end
+
+-- backslash-escaped glob stays literal
+do
+  local r = `echo \*.c`
+  local out = r.stdout:gsub("\n$", "")
+  assert(out == "*.c", "backslash-escaped glob expanded: " .. out)
+end
+
+
+-- === brace expansion ===
+
+do
+  local r = `echo {a,b,c}`
+  local out = r.stdout:gsub("\n$", "")
+  assert(out == "a b c", "brace expansion failed, got: " .. out)
+end
+
+-- brace with prefix
+do
+  local r = `echo hello{world,there}`
+  local out = r.stdout:gsub("\n$", "")
+  assert(out == "helloworld hellothere",
+         "brace prefix expansion failed, got: " .. out)
+end
+
+-- space inside braces: no expansion (treated as separate tokens)
+do
+  local r = `echo {a, b}`
+  local out = r.stdout:gsub("\n$", "")
+  -- with space after comma, the shell splits into tokens "{a," and "b}"
+  assert(out == "{a, b}", "space-in-braces should not expand, got: " .. out)
+end
+
+
+-- === tilde expansion ===
+
+-- ~ expands to $HOME
+do
+  local home = os.getenv("HOME")
+  local r = `echo ~`
+  local out = r.stdout:gsub("\n$", "")
+  assert(out == home, "~ did not expand to HOME, got: " .. out)
+end
+
+-- ~/path expands to $HOME/path
+do
+  local home = os.getenv("HOME")
+  local r = `echo ~/foo`
+  local out = r.stdout:gsub("\n$", "")
+  assert(out == home .. "/foo",
+         "~/foo did not expand, got: " .. out)
+end
+
+-- quoted ~ stays literal
+do
+  local r = `echo "~"`
+  local out = r.stdout:gsub("\n$", "")
+  assert(out == "~", "quoted ~ expanded: " .. out)
+end
+
+-- cd ~ should work (builtin receives expanded path)
+do
+  local before = `pwd`.stdout:gsub("\n$", "")
+  local home = os.getenv("HOME")
+  local r = `cd ~`
+  assert(r.code == 0, "cd ~ failed: " .. r.stderr)
+  local after = `pwd`.stdout:gsub("\n$", "")
+  assert(after == home, "cd ~ did not go home, got: " .. after)
+  `cd ${before}`
+end
+
+
+-- === expansion in pipelines ===
+
+do
+  local r = `echo *.c | head -1`
+  local out = r.stdout:gsub("\n$", "")
+  -- pipeline should have expanded *.c before piping
+  assert(out ~= "*.c", "glob not expanded in pipeline, got: " .. out)
+end
+
+
+print "OK"