feat: use configurable path to lefthook (LEFTHOOK_BIN) (#653)

* turn on trace output in git hook when LEFTHOOK_VERBOSE is set
* add support to giving an explicit path to lefthook in git hook. useful for developing
* Document LEFTHOOK_PATH
* Switch to LEFTHOOK_BIN

docs/usage.md

@@ -18,6 +18,7 @@ Then use git as usually, you don't need to reinstall lefthook when you change th
   - [`LEFTHOOK_EXCLUDE`](#lefthook_exclude)
   - [`LEFTHOOK_QUIET`](#lefthook_quiet)
   - [`LEFTHOOK_VERBOSE`](#lefthook_verbose)
+  - [`LEFTHOOK_BIN`](#lefthook_bin)
 - [Features and tips](#features-and-tips)
   - [Disable lefthook in CI](#disable-lefthook-in-ci)
   - [Local config](#local-config)
@@ -192,6 +193,15 @@ SUMMARY: (done in 0.01 seconds)
 
 Set `LEFTHOOK_VERBOSE=1` or `LEFTHOOK_VERBOSE=true` to enable verbose printing.
 
+### `LEFTHOOK_BIN`
+
+Set `LEFTHOOK_BIN` to a location where lefthook is installed to use that instead of trying to detect from the it the PATH or from a package manager.
+
+Useful for cases when:
+
+- lefthook is installed multiple ways, and you want to be explicit about which one is used (example: installed through homebrew, but also is in Gemfile but you are using a ruby version manager like rbenv that prepends it to the path)
+- debugging and/or developing lefthook
+
 ## Features and tips
 
 ### Disable lefthook in CI

internal/templates/hook.tmpl

@@ -1,5 +1,9 @@
 #!/bin/sh
 
+if [ "$LEFTHOOK_VERBOSE" = "1" -o "$LEFTHOOK_VERBOSE" = "true" ]; then
+  set -x
+fi
+
 if [ "$LEFTHOOK" = "0" ]; then
   exit 0
 fi
@@ -15,7 +19,10 @@ call_lefthook()
   osArch=$(uname | tr '[:upper:]' '[:lower:]')
   cpuArch=$(uname -m | sed 's/aarch64/arm64/')
 
-  if lefthook{{.Extension}} -h >/dev/null 2>&1
+  if test -n "$LEFTHOOK_BIN"
+  then
+    "$LEFTHOOK_BIN" "$@"
+  elif lefthook{{.Extension}} -h >/dev/null 2>&1
   then
     lefthook{{.Extension}} "$@"
   {{if .Extension -}}