doc: update references to renamed AsciiDoc files

The .txt extensions were changed to .adoc in 1f010d6 (doc: use .adoc
extension for AsciiDoc files, 2025-01-20). References to the renamed
files were not updated yet.

Signed-off-by: Jouke Witteveen <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: joukewitteveen

Documentation/gitprotocol-v2.adoc

@@ -54,7 +54,7 @@ In general a client can request to speak protocol v2 by sending
 `version=2` through the respective side-channel for the transport being
 used which inevitably sets `GIT_PROTOCOL`.  More information can be
 found in linkgit:gitprotocol-pack[5] and linkgit:gitprotocol-http[5], as well as the
-`GIT_PROTOCOL` definition in `git.txt`. In all cases the
+`GIT_PROTOCOL` definition in `git.adoc`. In all cases the
 response from the server is the capability advertisement.
 
 Git Transport
@@ -99,7 +99,7 @@ Uses the `--http-backend-info-refs` option to
 linkgit:git-upload-pack[1].
 
 The server may need to be configured to pass this header's contents via
-the `GIT_PROTOCOL` variable. See the discussion in `git-http-backend.txt`.
+the `GIT_PROTOCOL` variable. See the discussion in `git-http-backend.adoc`.
 
 Capability Advertisement
 ------------------------

Documentation/technical/build-systems.adoc

@@ -32,7 +32,7 @@ that generally have somebody running test pipelines against regularly:
   - OpenBSD
 
 The platforms which must be supported by the tool should be aligned with our
-[platform support policy](platform-support.txt).
+xref:platform-support.adoc[platform support policy].
 
 === Auto-detection of supported features
 

contrib/subtree/README

@@ -1,5 +1,5 @@
 
-Please read git-subtree.txt for documentation.
+Please read git-subtree.adoc for documentation.
 
 Please don't contact me using github mail; it's slow, ugly, and worst of
 all, redundant. Email me instead at [email protected] and I'll be happy to

mergetools/vimdiff

@@ -274,8 +274,8 @@ gen_cmd () {
 	# definition.
 	#
 	# The syntax of the "layout definitions" is explained in "Documentation/
-	# mergetools/vimdiff.txt" but you can already intuitively understand how
-	# it works by knowing that...
+	# mergetools/vimdiff.adoc" but you can already intuitively understand
+	# how it works by knowing that...
 	#
 	#   * "+" means "a new vim tab"
 	#   * "/" means "a new vim horizontal split"

sub-process.h

@@ -73,7 +73,7 @@ static inline struct child_process *subprocess_get_child_process(
 
 /*
  * Perform the version and capability negotiation as described in the
- * "Handshake" section of long-running-process-protocol.txt using the
+ * "Handshake" section of long-running-process-protocol.adoc using the
  * given requested versions and capabilities. The "versions" and "capabilities"
  * parameters are arrays terminated by a 0 or blank struct.
  *