Unify include guards to #pragma once

Traditional #ifndef guards are verbose, error-prone (copy-paste of
wrong macro names), and add noise to diffs. #pragma once is supported
by all compilers we target and eliminates these issues.

- Convert 489 headers from #ifndef guards to #pragma once
- Add #pragma once to 5 headers that had no guard at all
- Skip src/eckit/contrib/ (third-party code)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: Ozaq

src/eckit/bases/Loader.h

@@ -11,9 +11,7 @@
 // File Loader.h
 // Baudouin Raoult - ECMWF Jul 96
 
-#ifndef eckit_Loader_h
-#define eckit_Loader_h
-
+#pragma once
 #include "eckit/eckit.h"
 
 #include "eckit/container/ClassExtent.h"
@@ -41,5 +39,3 @@ class Loader : public ClassExtent<Loader> {
 //-----------------------------------------------------------------------------
 
 }  // namespace eckit
-
-#endif

src/eckit/bases/Watcher.h

@@ -11,9 +11,7 @@
 // File Watcher.h
 // Baudouin Raoult - ECMWF Jun 98
 
-#ifndef eckit_Watcher_h
-#define eckit_Watcher_h
-
+#pragma once
 //-----------------------------------------------------------------------------
 
 namespace eckit {
@@ -36,5 +34,3 @@ class Watcher {
 //-----------------------------------------------------------------------------
 
 }  // namespace eckit
-
-#endif

src/eckit/cmd/AliasCmd.h

@@ -11,9 +11,7 @@
 /// @author Manuel Fuentes
 /// @date   Jan 1997
 
-#ifndef eckit_cmd_AliasCmd_H
-#define eckit_cmd_AliasCmd_H
-
+#pragma once
 #include "eckit/cmd/CmdResource.h"
 
 
@@ -52,5 +50,3 @@ class AliasCmd : public CmdResource {
 //----------------------------------------------------------------------------------------------------------------------
 
 }  // namespace eckit
-
-#endif

src/eckit/cmd/Arg.h

@@ -11,9 +11,7 @@
 /// @author Manuel Fuentes
 /// @date   Jan 1997
 
-#ifndef eckit_cmd_Arg_H
-#define eckit_cmd_Arg_H
-
+#pragma once
 #include <iosfwd>
 #include <memory>
 #include <string>
@@ -90,5 +88,3 @@ class Arg {
 //-----------------------------------------------------------------------------
 
 }  // namespace eckit
-
-#endif

src/eckit/cmd/CmdApplication.h

@@ -12,9 +12,7 @@
 /// @author Florian Rathgeber
 /// @date   June 2015
 
-#ifndef eckit_cmd_CmdApplication_H
-#define eckit_cmd_CmdApplication_H
-
+#pragma once
 #include "eckit/cmd/CmdParser.h"
 
 namespace eckit {
@@ -45,5 +43,3 @@ class CmdApplication : public Prompter {
 //----------------------------------------------------------------------------------------------------------------------
 
 }  // namespace eckit
-
-#endif

src/eckit/cmd/CmdArg.h

@@ -8,9 +8,7 @@
  * nor does it submit to any jurisdiction.
  */
 
-#ifndef eckit_cmd_CmdArg_H
-#define eckit_cmd_CmdArg_H
-
+#pragma once
 #include "eckit/config/Resource.h"
 #include "eckit/serialisation/Streamable.h"
 #include "eckit/value/Value.h"
@@ -115,5 +113,3 @@ class CmdArg : public eckit::Streamable {
 //-----------------------------------------------------------------------------
 
 }  // namespace eckit
-
-#endif

src/eckit/cmd/CmdParser.h

@@ -12,9 +12,7 @@
 /// @author Florian Rathgeber
 /// @date   June 2015
 
-#ifndef eckit_cmd_CmdParser_H
-#define eckit_cmd_CmdParser_H
-
+#pragma once
 #include <iostream>
 #include <vector>
 
@@ -100,5 +98,3 @@ class CmdParser {
 //-----------------------------------------------------------------------------
 
 }  // namespace eckit
-
-#endif

src/eckit/cmd/CmdResource.h

@@ -8,9 +8,7 @@
  * nor does it submit to any jurisdiction.
  */
 
-#ifndef eckit_cmd_CmdResource_H
-#define eckit_cmd_CmdResource_H
-
+#pragma once
 #include "eckit/cmd/Arg.h"
 #include "eckit/cmd/CmdArg.h"
 #include "eckit/eckit.h"
@@ -82,5 +80,3 @@ class CmdResource {
 
 
 }  // namespace eckit
-
-#endif

src/eckit/cmd/ConfigCmd.h

@@ -12,9 +12,7 @@
 /// @author Baudouin Raoult
 /// @date   Jan 1997
 
-#ifndef eckit_cmd_ConfigCmd_H
-#define eckit_cmd_ConfigCmd_H
-
+#pragma once
 #include "eckit/cmd/CmdResource.h"
 
 //-----------------------------------------------------------------------------
@@ -54,5 +52,3 @@ class ConfigCmd : public CmdResource {
 //-----------------------------------------------------------------------------
 
 }  // namespace eckit
-
-#endif

src/eckit/cmd/DirCmd.h

@@ -12,9 +12,7 @@
 /// @author Baudouin Raoult
 /// @date   Jan 1997
 
-#ifndef eckit_cmd_DirCmd_H
-#define eckit_cmd_DirCmd_H
-
+#pragma once
 #include "eckit/cmd/CmdResource.h"
 
 //-----------------------------------------------------------------------------
@@ -54,5 +52,3 @@ class DirCmd : public CmdResource {
 //-----------------------------------------------------------------------------
 
 }  // namespace eckit
-
-#endif