Smart xswiftbus compatibility check based on git commit SHA-1

This is more tolerant that the simple check based on version numbers.
Different versions can be compatible if they have the same SHA-1 when
considering only those files that can influence xswiftbus.

src/xswiftbus/service.cpp

@@ -58,6 +58,11 @@ namespace XSwiftBus
         return version;
     }
 
+    std::string CService::getCommitHash() const
+    {
+        return XSWIFTBUS_COMMIT;
+    }
+
     void CService::addTextMessage(const std::string &text, double red, double green, double blue)
     {
         if (text.empty()) { return; }
@@ -253,6 +258,13 @@ namespace XSwiftBus
                     sendDBusReply(sender, serial, getVersionNumber());
                 });
             }
+            else if (message.getMethodName() == "getCommitHash")
+            {
+                queueDBusCall([ = ]()
+                {
+                    sendDBusReply(sender, serial, getCommitHash());
+                });
+            }
             else if (message.getMethodName() == "addTextMessage")
             {
                 maybeSendEmptyDBusReply(wantsReply, sender, serial);

src/xswiftbus/service.h

@@ -62,6 +62,9 @@ namespace XSwiftBus
         //! Returns the XSwiftBus version number
         std::string getVersionNumber() const;
 
+        //! Returns the SHA1 of the last commit that could influence xswiftbus.
+        std::string getCommitHash() const;
+
         //! Add a text message to the on-screen display, with RGB components in the range [0,1]
         void addTextMessage(const std::string &text, double red, double green, double blue);
 

src/xswiftbus/version.pri

@@ -0,0 +1,10 @@
+# this file is included by swift.pro in the project root
+
+XSWIFTBUS_DEPENDENTS = $$SourceRoot/src/xswiftbus \
+    $$SourceRoot/src/blackmisc/simulation/xplane/qtfreeutils.* \
+    $$SourceRoot/src/blackmisc/simulation/settings/xswiftbussettingsqtfree.*
+
+XSWIFTBUS_COMMIT = $$system(git log -n 1 --format=%h -- $$XSWIFTBUS_DEPENDENTS)
+
+# make the variable available in other files without needing to be included
+cache(XSWIFTBUS_COMMIT)

src/xswiftbus/xswiftbus.pro

@@ -86,6 +86,9 @@ isEmpty(GIT_BIN) {
 DEFINES += XSWIFTBUS_VERSION=\\\"$$swiftConfig(version.full)\\\"
 DEFINES += GIT_COMMIT_TS=\\\"$$GIT_COMMIT_TS\\\"
 
+isEmpty(XSWIFTBUS_COMMIT): error(Missing XSWIFTBUS_COMMIT variable)
+DEFINES += XSWIFTBUS_COMMIT=\\\"$$XSWIFTBUS_COMMIT\\\"
+
 # X-Plane plugins must follow a prescribed filename and directory structure.
 TARGET_EXT = .xpl
 win32:TARGET = win