The .txt extensions were changed to .adoc in 1f010d6bdf (doc: use .adoc
extension for AsciiDoc files, 2025-01-20).

Do the same for contrib/subtree.

Signed-off-by: Todd Zullinger <redacted>
---
 contrib/subtree/Makefile                              | 2 +-
 contrib/subtree/{git-subtree.txt => git-subtree.adoc} | 0
 2 files changed, 1 insertion(+), 1 deletion(-)
 rename contrib/subtree/{git-subtree.txt => git-subtree.adoc} (100%)

diff --git a/contrib/subtree/Makefile b/contrib/subtree/Makefile
index 8fe0bfd401..c0c9f21cb7 100644
--- a/contrib/subtree/Makefile
+++ b/contrib/subtree/Makefile

@@ -50,7 +50,7 @@ GIT_SUBTREE    := git-subtree
 
 GIT_SUBTREE_DOC := git-subtree.1
 GIT_SUBTREE_XML := git-subtree.xml
-GIT_SUBTREE_TXT := git-subtree.txt
+GIT_SUBTREE_TXT := git-subtree.adoc
 GIT_SUBTREE_HTML := git-subtree.html
 GIT_SUBTREE_TEST := ../../git-subtree
 

diff --git a/contrib/subtree/git-subtree.txt b/contrib/subtree/git-subtree.adoc
similarity index 100%
rename from contrib/subtree/git-subtree.txt
rename to contrib/subtree/git-subtree.adoc
-- 
2.49.0.rc0