[PATCH v3 24/63] docs/qapi-domain: add :unstable: directive option

[John Snow]

Although "unstable" is a feature (and *will* appear in the features
list), add a special :unstable: option to generate an eye-catch that
makes this information very hard to miss.

The forthcoming Transmogrifier in qapidoc.py will add this option
whenever it detects that the features list attached to a definition
contains the "unstable" entry.

Signed-off-by: Harmonie Snow <harmo...@gmail.com>
Signed-off-by: John Snow <js...@redhat.com>
---
 docs/sphinx-static/theme_overrides.css | 6 +++++-
 docs/sphinx/qapi_domain.py             | 8 ++++++++
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/docs/sphinx-static/theme_overrides.css 
b/docs/sphinx-static/theme_overrides.css
index 3765cab1b20..5f58f1d5246 100644
--- a/docs/sphinx-static/theme_overrides.css
+++ b/docs/sphinx-static/theme_overrides.css
@@ -221,7 +221,7 @@ div[class^="highlight"] pre {
     margin: 0.25em;
 }
 
-.qapi-deprecated {
+.qapi-deprecated,.qapi-unstable {
     background-color: #fffef5;
     border: solid #fff176 6px;
     font-weight: bold;
@@ -230,6 +230,10 @@ div[class^="highlight"] pre {
     margin: 5px;
 }
 
+.qapi-unstable::before {
+    content: '🚧 ';
+}
+
 .qapi-deprecated::before {
     content: '⚠️ ';
 }
diff --git a/docs/sphinx/qapi_domain.py b/docs/sphinx/qapi_domain.py
index b672ae6c504..00fd11ebf79 100644
--- a/docs/sphinx/qapi_domain.py
+++ b/docs/sphinx/qapi_domain.py
@@ -218,6 +218,7 @@ class QAPIObject(QAPIDescription):
             # These are QAPI originals:
             "since": directives.unchanged,
             "deprecated": directives.flag,
+            "unstable": directives.flag,
         }
     )
 
@@ -300,6 +301,13 @@ def _add_pip(source: str, content: str, classname: str) -> 
None:
                 "qapi-deprecated",
             )
 
+        if "unstable" in self.options:
+            _add_pip(
+                ":unstable:",
+                f"This {self.objtype} is unstable/experimental.",
+                "qapi-unstable",
+            )
+
         if infopips.children:
             contentnode.insert(0, infopips)
 
-- 
2.48.1