debugging - Looking for guidance to get `gist.el` up and running -- errors -

can please steer me in right direction getting gist.el work properly. here error message:

debugger entered--lisp error: (wrong-type-argument stringp nil)   call-process(nil nil #<buffer  *string-output*> nil "config" "github.user")   apply(call-process nil nil #<buffer  *string-output*> nil ("config" "github.user"))   process-file(nil nil #<buffer  *string-output*> nil "config" "github.user")   apply(process-file nil nil #<buffer  *string-output*> nil ("config" "github.user"))   (let ((standard-output standard-output)) (apply (quote process-file) git nil standard-output nil args))   (progn (let ((standard-output standard-output)) (apply (quote process-file) git nil standard-output nil args)) (save-current-buffer (set-buffer standard-output) (buffer-string)))   (unwind-protect (progn (let ((standard-output standard-output)) (apply (quote process-file) git nil standard-output nil args)) (save-current-buffer (set-buffer standard-output) (buffer-string))) (kill-buffer standard-output))   (let ((standard-output (get-buffer-create (generate-new-buffer-name " *string-output*")))) (unwind-protect (progn (let ((standard-output standard-output)) (apply (quote process-file) git nil standard-output nil args)) (save-current-buffer (set-buffer standard-output) (buffer-string))) (kill-buffer standard-output)))   (let ((git (executable-find "git"))) (let ((standard-output (get-buffer-create (generate-new-buffer-name " *string-output*")))) (unwind-protect (progn (let ((standard-output standard-output)) (apply (quote process-file) git nil standard-output nil args)) (save-current-buffer (set-buffer standard-output) (buffer-string))) (kill-buffer standard-output))))   gh-command-to-string("config" "github.user")   (funcall strip (gh-command-to-string "config" (gh-namespaced-key key)))   (let ((strip (function (lambda (string) (if (> (length string) 0) (substring string 0 (- ... 1))))))) (funcall strip (gh-command-to-string "config" (gh-namespaced-key key))))   gh-config("user")   (or (plist-get (cdr (assoc profile gh-auth-alist)) :username) (plist-get (cdr (assoc profile gh-profile-alist)) :username) (gh-config "user"))   (let* ((profile (gh-profile-current-profile)) (user (or (plist-get (cdr (assoc profile gh-auth-alist)) :username) (plist-get (cdr (assoc profile gh-profile-alist)) :username) (gh-config "user")))) (if (not user) (progn (setq user (read-string "github username: ")) (gh-set-config "user" user))) (gh-auth-remember profile :username user) user)   gh-auth-get-username()   (eieio-oset obj (quote :username) (gh-auth-get-username))   (or (eieio-oref obj (quote :username)) (eieio-oset obj (quote :username) (gh-auth-get-username)))   (let ((obj (call-next-method))) (or (eieio-oref obj (quote :username)) (eieio-oset obj (quote :username) (gh-auth-get-username))) obj)   gh-authenticator(gh-oauth-authenticator "auth")   apply(gh-authenticator (gh-oauth-authenticator "auth"))   call-next-method()   (let ((obj (call-next-method))) (or (eieio-oref obj (quote :token)) (eieio-oset obj (quote :token) (gh-auth-get-oauth-token))) obj)   gh-oauth-authenticator(gh-oauth-authenticator "auth")   apply(gh-oauth-authenticator (gh-oauth-authenticator "auth"))   eieio-generic-call(constructor (gh-oauth-authenticator "auth"))   constructor(gh-oauth-authenticator "auth")   apply(constructor gh-oauth-authenticator "auth" nil)   gh-oauth-authenticator("auth")   funcall(gh-oauth-authenticator "auth")   (or (eieio-oref obj (quote :auth)) (funcall gh-api-v3-authenticator "auth"))   (gh-api-set-default-auth obj (or (eieio-oref obj (quote :auth)) (funcall gh-api-v3-authenticator "auth")))   (let ((obj (call-next-method)) (gh-profile-current-profile (gh-profile-current-profile))) (eieio-oset obj (quote :profile) (gh-profile-current-profile)) (eieio-oset obj (quote :base) (gh-profile-url)) (gh-api-set-default-auth obj (or (eieio-oref obj (quote :auth)) (funcall gh-api-v3-authenticator "auth"))) obj)   gh-api-v3(gh-gist-api "api" :sync nil :cache t :num-retries 1)   apply(gh-api-v3 (gh-gist-api "api" :sync nil :cache t :num-retries 1))   eieio-generic-call(constructor (gh-gist-api "api" :sync nil :cache t :num-retries 1))   constructor(gh-gist-api "api" :sync nil :cache t :num-retries 1)   apply(constructor gh-gist-api "api" (:sync nil :cache t :num-retries 1))   gh-gist-api("api" :sync nil :cache t :num-retries 1)   (let ((gh-profile-current-profile (or gh-profile-current-profile (gh-profile-completing-read)))) (gh-gist-api "api" :sync sync :cache t :num-retries 1))   gist-get-api(nil)   (let* ((gh-profile-current-profile (or gh-profile-current-profile (gh-profile-completing-read))) (bufname (format "*%s:gists*" gh-profile-current-profile)) (api (gist-get-api nil))) (if force-reload (progn (pcache-clear (eieio-oref api (quote :cache))) (or background (message "retrieving list of gists...")))) (if (and background (not (get-buffer bufname))) nil (let ((resp (gh-gist-list api))) (gh-url-add-response-callback resp (let ((--cl-buffer-- (make-symbol "--buffer--"))) (let* ((v --cl-buffer--)) (set v bufname)) (list (quote lambda) (quote (&rest --cl-rest--)) (list (quote apply) (list ... ...) (list ... --cl-buffer--) (quote --cl-rest--))))) (gh-url-add-response-callback resp (let ((--cl-profile-- (make-symbol "--profile--")) (--cl-buffer-- (make-symbol "--buffer--"))) (progn (let* (...) (set v ...)) (let* (...) (set v bufname))) (list (quote lambda) (quote (&rest --cl-rest--)) (list (quote apply) (list ... ...) (list ... --cl-buffer--) (list ... --cl-profile--) (quote --cl-rest--))))))))   gist-list(nil)   call-interactively(gist-list record nil)   command-execute(gist-list record)   (let ((prefix-arg prefixarg)) (command-execute function (quote record)))   (progn (let ((prefix-arg prefixarg)) (command-execute function (quote record))))   (if function (progn (let ((prefix-arg prefixarg)) (command-execute function (quote record)))))   (let* ((function (and (stringp command-name) (intern-soft command-name))) (binding (and suggest-key-bindings (not executing-kbd-macro) (where-is-internal function overriding-local-map t)))) (setq this-command function) (setq real-this-command function) (if function (progn (let ((prefix-arg prefixarg)) (command-execute function (quote record))))))   lawlist-execute-extended-command(nil "gist-list")   call-interactively(lawlist-execute-extended-command nil nil)   command-execute(lawlist-execute-extended-command) 

it looks (executable-find "git") returned nil, , caused error see. problem program git not in exec-path.

you can down debugger stack, starting noticing first arg call-process needs string (a process name). (use c-h f call-process learn this.)