[PATCH v2 2/2] doc: format-rev: use [synopsis] on code block

From: Kristoffer Haugsbakk <redacted>

This code block uses the placeholder `<subject>`. Let’s highlight this
placeholder properly by using the `synopsis` block definition which was
introduced in a34d1d53 (doc: convert git-show to synopsis style,
2026-02-06).

Yes, note that code blocks since commit a34d1d53 can, on synopsis-style
docs like this one, be immediately preceded by `[synopsis]`, just like
the command synopsis is:

    [synopsis]
    (EXPERIMENTAL!) git format-rev - [...]

Cf. verse-style:

    [verse]
    'git name-rev' [...]

Signed-off-by: Kristoffer Haugsbakk <redacted>
---

Notes (series):
    v2:
    • Add a paragraph to contrast synopsis code blocks with synopsis
      command description after talk with Patrick on v1[1]
    
      🔗 1: https://lore.kernel.org/git/ansWZxZ6lB0tYIJD@pks.im/ (local)

 Documentation/git-format-rev.adoc | 1 +
 1 file changed, 1 insertion(+)

diff --git a/Documentation/git-format-rev.adoc b/Documentation/git-format-rev.adoc
index 19241837345..d6c2e4aec1a 100644
--- a/Documentation/git-format-rev.adoc
+++ b/Documentation/git-format-rev.adoc

@@ -96,6 +96,7 @@ The mode `--stdin-mode=text` replaces each object name with the
 formatted commit, i.e. the format `"%s"` would transform some commit
 object name to `"<subject>"` without any termination. Like this:
 
+[synopsis]
 ----
 Did we not fix this in "<subject>"?
 ----

-- 
2.54.0.22.g9e26862b904