Make version available through $kak_version and debug info

.gitignore

@@ -6,6 +6,7 @@
 src/kak
 src/kak.debug
 src/kak.opt
+src/.version*
 doc/kak.1
 doc/kak.1.gz
 doc/manpages/*.gz

doc/pages/expansions.asciidoc

@@ -102,6 +102,9 @@ informations about Kakoune's state:
 *kak_config*::
     directory containing the user configuration
 
+*kak_version*::
+    version of the current Kakoune server (git hash or release name)
+
 *kak_count*::
     count parameter passed to the command
 

src/commands.cc

@@ -45,6 +45,8 @@
 namespace Kakoune
 {
 
+extern const char* version;
+
 namespace
 {
 
@@ -1146,6 +1148,7 @@ const CommandDesc debug_cmd = {
     {
         if (parser[0] == "info")
         {
+            write_to_debug_buffer(format("version: {}", version));
             write_to_debug_buffer(format("pid: {}", getpid()));
             write_to_debug_buffer(format("session: {}", Server::instance().session()));
             #ifdef KAK_DEBUG

src/main.cc

@@ -37,6 +37,8 @@
 namespace Kakoune
 {
 
+extern const char* version;
+
 static const char* startup_info =
 "Kakoune recent breaking changes:\n"
 " * Highlighters have been refactored to be part of scopes\n"
@@ -122,6 +124,10 @@ static const EnvVarDesc builtin_env_vars[] = { {
         "config", false,
         [](StringView name, const Context& context)
         { return config_directory(); }
+    }, {
+        "version", false,
+        [](StringView name, const Context& context) -> String
+        { return version; }
     }, {
         "opt_", true,
         [](StringView name, const Context& context)
@@ -671,7 +677,7 @@ int run_server(StringView session, StringView server_init,
                 });
 
             if (flags & ServerFlags::StartupInfo)
-                local_client->info_show("Welcome to Kakoune", startup_info, {}, InfoStyle::Prompt);
+                local_client->info_show(format("Kakoune {}", version), startup_info, {}, InfoStyle::Prompt);
         }
 
         while (not terminate and