add a wrapper for ssh-keygen

standalone/windows/ssh-keygen.cmd

@@ -0,0 +1,31 @@
+@rem Do not use "echo off" to not affect any child calls.
+
+@rem Enable extensions, the `verify other 2>nul` is a trick from the setlocal help
+@verify other 2>nul
+@setlocal enableDelayedExpansion
+@if errorlevel 1 (
+    @echo Unable to enable delayed expansion. Immediate expansion will be used.
+    @goto fallback
+)
+
+@rem Get the absolute path to the parent directory, which is assumed to be the
+@rem Git installation root.
+@for /F "delims=" %%I in ("%~dp0..") do @set git_install_root=%%~fI
+@set PATH=!git_install_root!\bin;!git_install_root!\mingw\bin;!PATH!
+
+ssh-keygen %*
+@goto end
+
+:fallback
+@rem The above script again with immediate expansion, in case delayed expansion
+@rem is unavailable.
+@for /F "delims=" %%I in ("%~dp0..") do @set git_install_root=%%~fI
+@set PATH=%git_install_root%\bin;%git_install_root%\mingw\bin;%PATH%
+
+@if not exist "%HOME%" @set HOME=%HOMEDRIVE%%HOMEPATH%
+@if not exist "%HOME%" @set HOME=%USERPROFILE%
+
+ssh-keygen %*
+
+:end
+@rem End of script