Hook into Windows' SSH Agent under WSL

This will securely store SSH key in the host system, tied to your user
account, will be locked when Windows is locked, and will avoid having to
type SSH passphrase in every new window you open.

shells/common/wsl.sh

@@ -0,0 +1,28 @@
+if [ -n ${WSL_DISTRO_NAME:-} ] || grep -sqi microsoft /proc/sys/kernel/osrelease; then
+    # # Talk to Windows' SSH-Agent when under WSL, using https://github.com/rupor-github/wsl-ssh-agent
+    # # wsl-ssh-agent started with:
+    # #
+    # #    wsl-ssh-agent-gui.exe -setenv -envname=WSL_AUTH_SOCK -lemonade=2489;127.0.0.1/24
+    # #
+    # [ -n ${WSL_AUTH_SOCK} ] && export SSH_AUTH_SOCK=${WSL_AUTH_SOCK}
+
+    # Above does not work currently due to WSL1 -> WSL2 turbulence. Workaround below.
+    # Based on: https://github.com/rupor-github/wsl-ssh-agent/tree/4e08e3fa84380f4d62bfdf607ae6b2c680e1ff3e#wsl-2-compatibility
+
+    # where I installed it (must be on Windows' filesystem)
+    NPIPERELAY_DIR="/mnt/c/Program Files/WSL-SSH-Agent"
+
+    export SSH_AUTH_SOCK=$HOME/.ssh/agent.sock
+
+    ss -a | grep -q $SSH_AUTH_SOCK
+
+    if [ $? -ne 0 ]; then
+        rm -f $SSH_AUTH_SOCK
+        ( 
+            PATH="$NPIPERELAY_DIR:$PATH"
+            setsid socat \
+                UNIX-LISTEN:$SSH_AUTH_SOCK,fork \
+                EXEC:"npiperelay.exe -ei -s //./pipe/openssh-ssh-agent",nofork & 
+        ) >/dev/null 2>&1
+    fi
+fi