Make the :doc command work even if lf is not in the PATH, add `lf…

…` environment variable (#1176)

* Export a `$lf` environment variable with path to lf binary

If Go fails to find a path to the lf binary, `$lf` is set to the string `lf` so
that running `$lf` in scripts gives a reasonable error message.

* Make the `:doc` command work even if lf is not in the PATH

Previously, `:doc` executed `lf -doc`. Now, it executed `$lf -doc` or `%lf%
-doc`.

Before this change, `:doc` did not work if `lf` is not in the PATH. This is
likely to happen to new users who are trying out `lf` and need docs the most.

Moreover, if you made some changes to the docs and ran `lf` with `go run .`,
`:doc` would return the docs for the version of `lf` in the PATH instead of
what is expected.

doc.go

@@ -933,19 +933,23 @@ For example, with POSIX shells, you can use '[ -n "$LF_LEVEL" ] && PS1="$PS1""(l
 
 	OPENER
 
-If this variable is set in the environment, use the same value, otherwise set the value to 'start' in Windows, 'open' in MacOS, 'xdg-open' in others.
+If this variable is set in the environment, use the same value. Otherwise, this is set to 'start' in Windows, 'open' in MacOS, 'xdg-open' in others.
 
 	EDITOR
 
-If this variable is set in the environment, use the same value, otherwise set the value to 'vi' on Unix, 'notepad' in Windows.
+If this variable is set in the environment, use the same value. Otherwise, this is set to 'vi' on Unix, 'notepad' in Windows.
 
 	PAGER
 
-If this variable is set in the environment, use the same value, otherwise set the value to 'less' on Unix, 'more' in Windows.
+If this variable is set in the environment, use the same value. Otherwise, this is set to 'less' on Unix, 'more' in Windows.
 
 	SHELL
 
-If this variable is set in the environment, use the same value, otherwise set the value to 'sh' on Unix, 'cmd' in Windows.
+If this variable is set in the environment, use the same value. Otherwise, this is set to 'sh' on Unix, 'cmd' in Windows.
+
+	lf
+
+Absolute path to the currently running lf binary, if it can be found. Otherwise, this is set to the string 'lf'.
 
 	lf_{option}
 

lf.1

@@ -1130,25 +1130,31 @@ The value of this variable is set to the current nesting level when you run lf f
     OPENER
 .EE
 .PP
-If this variable is set in the environment, use the same value, otherwise set the value to 'start' in Windows, 'open' in MacOS, 'xdg-open' in others.
+If this variable is set in the environment, use the same value. Otherwise, this is set to 'start' in Windows, 'open' in MacOS, 'xdg-open' in others.
 .PP
 .EX
     EDITOR
 .EE
 .PP
-If this variable is set in the environment, use the same value, otherwise set the value to 'vi' on Unix, 'notepad' in Windows.
+If this variable is set in the environment, use the same value. Otherwise, this is set to 'vi' on Unix, 'notepad' in Windows.
 .PP
 .EX
     PAGER
 .EE
 .PP
-If this variable is set in the environment, use the same value, otherwise set the value to 'less' on Unix, 'more' in Windows.
+If this variable is set in the environment, use the same value. Otherwise, this is set to 'less' on Unix, 'more' in Windows.
 .PP
 .EX
     SHELL
 .EE
 .PP
-If this variable is set in the environment, use the same value, otherwise set the value to 'sh' on Unix, 'cmd' in Windows.
+If this variable is set in the environment, use the same value. Otherwise, this is set to 'sh' on Unix, 'cmd' in Windows.
+.PP
+.EX
+    lf
+.EE
+.PP
+Absolute path to the currently running lf binary, if it can be found. Otherwise, this is set to the string 'lf'.
 .PP
 .EX
     lf_{option}

main.go

@@ -79,6 +79,13 @@ func exportEnvVars() {
 	level++
 
 	os.Setenv("LF_LEVEL", strconv.Itoa(level))
+
+	lfPath, err := os.Executable()
+	if err != nil {
+		log.Printf("getting path to lf binary: %s", err)
+		lfPath = "lf"
+	}
+	os.Setenv("lf", lfPath)
 }
 
 // used by exportOpts below

os.go

@@ -159,7 +159,7 @@ func setDefaults() {
 	gOpts.keys["i"] = &execExpr{"$", `$PAGER "$f"`}
 	gOpts.keys["w"] = &execExpr{"$", "$SHELL"}
 
-	gOpts.cmds["doc"] = &execExpr{"$", "lf -doc | $PAGER"}
+	gOpts.cmds["doc"] = &execExpr{"$", `"$lf" -doc | $PAGER`}
 	gOpts.keys["<f-1>"] = &callExpr{"doc", nil, 1}
 }
 

os_windows.go

@@ -115,7 +115,7 @@ func setDefaults() {
 	gOpts.keys["i"] = &execExpr{"!", "%PAGER% %f%"}
 	gOpts.keys["w"] = &execExpr{"$", "%SHELL%"}
 
-	gOpts.cmds["doc"] = &execExpr{"!", "lf -doc | %PAGER%"}
+	gOpts.cmds["doc"] = &execExpr{"!", "%lf% -doc | %PAGER%"}
 	gOpts.keys["<f-1>"] = &callExpr{"doc", nil, 1}
 }