Merge branch 'sg/asciidoctor-in-ci'

Update our support to format documentation in the CI environment,
either with AsciiDoc ro Asciidoctor.

* sg/asciidoctor-in-ci:
  ci: fix AsciiDoc/Asciidoctor stderr check in the documentation build job
  ci: stick with Asciidoctor v1.5.8 for now
  ci: install Asciidoctor in 'ci/install-dependencies.sh'
  Documentation/technical/protocol-v2.txt: fix formatting
  Documentation/technical/api-config.txt: fix formatting
  Documentation/git-diff-tree.txt: fix formatting

3 files changed, 28 insertions, 27 deletions

diff --git a/Documentation/git-diff-tree.txt b/Documentation/git-diff-tree.txt
index 24f32e8c54..5c8a2a5e97 100644
--- a/Documentation/git-diff-tree.txt
+++ b/Documentation/git-diff-tree.txt
@@ -118,6 +118,7 @@ include::pretty-options.txt[]
 
 
 include::pretty-formats.txt[]
+
 include::diff-format.txt[]
 
 GIT
diff --git a/Documentation/technical/api-config.txt b/Documentation/technical/api-config.txt
index fa39ac9d71..7d20716c32 100644
--- a/Documentation/technical/api-config.txt
+++ b/Documentation/technical/api-config.txt
@@ -229,7 +229,7 @@ A `config_set` can be used to construct an in-memory cache for
 config-like files that the caller specifies (i.e., files like `.gitmodules`,
 `~/.gitconfig` etc.). For example,
 
----------------------------------------
+----------------------------------------
 struct config_set gm_config;
 git_configset_init(&gm_config);
 int b;
diff --git a/Documentation/technical/protocol-v2.txt b/Documentation/technical/protocol-v2.txt
index ead85ce35c..03264c7d9a 100644
--- a/Documentation/technical/protocol-v2.txt
+++ b/Documentation/technical/protocol-v2.txt
@@ -1,5 +1,5 @@
- Git Wire Protocol, Version 2
-==============================
+Git Wire Protocol, Version 2
+============================
 
 This document presents a specification for a version 2 of Git's wire
 protocol.  Protocol v2 will improve upon v1 in the following ways:
@@ -22,8 +22,8 @@ will be commands which a client can request be executed.  Once a command
 has completed, a client can reuse the connection and request that other
 commands be executed.
 
- Packet-Line Framing
----------------------
+Packet-Line Framing
+-------------------
 
 All communication is done using packet-line framing, just as in v1.  See
 `Documentation/technical/pack-protocol.txt` and
@@ -34,8 +34,8 @@ In protocol v2 these special packets will have the following semantics:
   * '0000' Flush Packet (flush-pkt) - indicates the end of a message
   * '0001' Delimiter Packet (delim-pkt) - separates sections of a message
 
- Initial Client Request
-------------------------
+Initial Client Request
+----------------------
 
 In general a client can request to speak protocol v2 by sending
 `version=2` through the respective side-channel for the transport being
@@ -43,22 +43,22 @@ used which inevitably sets `GIT_PROTOCOL`.  More information can be
 found in `pack-protocol.txt` and `http-protocol.txt`.  In all cases the
 response from the server is the capability advertisement.
 
- Git Transport
-~~~~~~~~~~~~~~~
+Git Transport
+~~~~~~~~~~~~~
 
 When using the git:// transport, you can request to use protocol v2 by
 sending "version=2" as an extra parameter:
 
    003egit-upload-pack /project.git\0host=myserver.com\0\0version=2\0
 
- SSH and File Transport
-~~~~~~~~~~~~~~~~~~~~~~~~
+SSH and File Transport
+~~~~~~~~~~~~~~~~~~~~~~
 
 When using either the ssh:// or file:// transport, the GIT_PROTOCOL
 environment variable must be set explicitly to include "version=2".
 
- HTTP Transport
-~~~~~~~~~~~~~~~~
+HTTP Transport
+~~~~~~~~~~~~~~
 
 When using the http:// or https:// transport a client makes a "smart"
 info/refs request as described in `http-protocol.txt` and requests that
@@ -79,8 +79,8 @@ A v2 server would reply:
 Subsequent requests are then made directly to the service
 `$GIT_URL/git-upload-pack`. (This works the same for git-receive-pack).
 
- Capability Advertisement
---------------------------
+Capability Advertisement
+------------------------
 
 A server which decides to communicate (based on a request from a client)
 using protocol version 2, notifies the client by sending a version string
@@ -101,8 +101,8 @@ to be executed by the client.
     key = 1*(ALPHA | DIGIT | "-_")
     value = 1*(ALPHA | DIGIT | " -_.,?\/{}[]()<>!@#$%^&*+=:;")
 
- Command Request
------------------
+Command Request
+---------------
 
 After receiving the capability advertisement, a client can then issue a
 request to select the command it wants with any particular capabilities
@@ -137,8 +137,8 @@ command be executed or can terminate the connection.  A client may
 optionally send an empty request consisting of just a flush-pkt to
 indicate that no more requests will be made.
 
- Capabilities
---------------
+Capabilities
+------------
 
 There are two different types of capabilities: normal capabilities,
 which can be used to to convey information or alter the behavior of a
@@ -153,8 +153,8 @@ management on the server side in order to function correctly.  This
 permits simple round-robin load-balancing on the server side, without
 needing to worry about state management.
 
- agent
-~~~~~~~
+agent
+~~~~~
 
 The server can advertise the `agent` capability with a value `X` (in the
 form `agent=X`) to notify the client that the server is running version
@@ -168,8 +168,8 @@ printable ASCII characters except space (i.e., the byte range 32 < x <
 and debugging purposes, and MUST NOT be used to programmatically assume
 the presence or absence of particular features.
 
- ls-refs
-~~~~~~~~~
+ls-refs
+~~~~~~~
 
 `ls-refs` is the command used to request a reference advertisement in v2.
 Unlike the current reference advertisement, ls-refs takes in arguments
@@ -199,8 +199,8 @@ The output of ls-refs is as follows:
     symref = "symref-target:" symref-target
     peeled = "peeled:" obj-id
 
- fetch
-~~~~~~~
+fetch
+~~~~~
 
 `fetch` is the command used to fetch a packfile in v2.  It can be looked
 at as a modified version of the v1 fetch where the ref-advertisement is
@@ -444,8 +444,8 @@ header.
 		2 - progress messages
 		3 - fatal error message just before stream aborts
 
- server-option
-~~~~~~~~~~~~~~~
+server-option
+~~~~~~~~~~~~~
 
 If advertised, indicates that any number of server specific options can be
 included in a request.  This is done by sending each option as a