chore: import upstream snapshot with attribution

internal/progress/mode.go

@@ -0,0 +1,75 @@
+package progress
+
+import (
+	"io"
+	"os"
+	"sync/atomic"
+
+	"golang.org/x/term"
+)
+
+// IsTTY reports whether w is backed by a terminal file descriptor.
+func IsTTY(w io.Writer) bool {
+	f, ok := w.(interface{ Fd() uintptr })
+	if !ok {
+		return false
+	}
+	return term.IsTerminal(int(f.Fd()))
+}
+
+func envDisablesColor() bool {
+	if os.Getenv("NO_COLOR") != "" {
+		return true
+	}
+	if t := os.Getenv("TERM"); t == "dumb" {
+		return true
+	}
+	return false
+}
+
+// animationAllowed decides whether w can host the animated renderer. The
+// contract matches the --no-progress help text: NO_COLOR, TERM=dumb, a
+// non-TTY writer, and CI all force plain output. On Windows it additionally
+// requires the console to accept VT processing (legacy conhost without VT
+// gets plain text rather than raw escape soup). GORTEX_FORCE_ANIMATION=1
+// overrides everything — it exists for demos and PTY-less frame capture.
+func animationAllowed(w io.Writer) bool {
+	if envFlag("GORTEX_FORCE_ANIMATION") {
+		return true
+	}
+	if !IsTTY(w) {
+		return false
+	}
+	if envDisablesColor() {
+		return false
+	}
+	if os.Getenv("CI") != "" {
+		return false
+	}
+	return enableVT(w)
+}
+
+// cursorHiddenOnStderr tracks whether an animated tracker writing to the
+// process stderr currently has the cursor hidden. RestoreTerminal uses it to
+// undo the hide from exit paths that bypass a tracker's own finish (fatal
+// errors, panics unwinding main).
+var cursorHiddenOnStderr atomic.Bool
+
+// RestoreTerminal re-shows the cursor and resets SGR state on stderr if an
+// animated tracker left the cursor hidden. Safe to call unconditionally and
+// repeatedly; a no-op when nothing needs restoring. Wire it into every
+// process exit path that can interrupt a live animation.
+func RestoreTerminal() {
+	if cursorHiddenOnStderr.CompareAndSwap(true, false) {
+		_, _ = os.Stderr.WriteString(ansiShowCursor + ansiReset)
+	}
+}
+
+func markCursorHidden(w io.Writer)   { setCursorFlag(w, true) }
+func markCursorRestored(w io.Writer) { setCursorFlag(w, false) }
+
+func setCursorFlag(w io.Writer, hidden bool) {
+	if f, ok := w.(*os.File); ok && f == os.Stderr {
+		cursorHiddenOnStderr.Store(hidden)
+	}
+}