CLI for a better "cd on quit"

Use `--print-pwd-as-result` to print the last working directory instead
of the focused or selected nodes, when you quit using the `PrintResultAndQuit`
message (i.e. by pressing `enter`).

This helps with implementing the "cd on quit" functionality using a plain shell
alias.

Example:

```
alias xcd='cd "$(xplr --print-pwd-as-result)"'
```

With this alias set, you can navigate directories using xplr by entering
`xcd` command, and when you quit by pressing enter, you will enter the
directory.

You can of course, quit with plain `Quit` (i.e. by pressing `esc`) to
gracefully cancel "cd on quit".

src/app.rs

@@ -2647,6 +2647,10 @@ impl App {
             .unwrap_or_default()
     }
 
+    pub fn pwd_str(&self) -> String {
+        format!("{}\n", &self.pwd)
+    }
+
     pub fn selection_str(&self) -> String {
         self.selection
             .iter()

src/bin/xplr.rs

@@ -27,7 +27,10 @@ fn main() {
                                       "$HOME/.config/xplr/init.lua")
     -C, --extra-config <PATH>...    Specifies extra config files to load
         --on-load <MESSAGE>...      Sends messages when xplr loads
-        --force-focus               Focuses on the given <PATH>, even if directory"###;
+        --force-focus               Focuses on the given <PATH>, even if it is
+                                      a directory
+        --print-pwd-as-result       Prints the last working directory when
+                                      quitting with `PrintResultAndQuit`"###;
 
         let args = r###"
     <PATH>            Path to focus on, or enter if directory, (default is `.`)

src/cli.rs

@@ -13,6 +13,7 @@ pub struct Cli {
     pub help: bool,
     pub read_only: bool,
     pub force_focus: bool,
+    pub print_pwd_as_result: bool,
     pub config: Option<PathBuf>,
     pub extra_config: Vec<PathBuf>,
     pub on_load: Vec<app::ExternalMsg>,
@@ -98,6 +99,10 @@ impl Cli {
                         cli.force_focus = true;
                     }
 
+                    "--print-pwd-as-result" => {
+                        cli.print_pwd_as_result = true;
+                    }
+
                     // path
                     path => {
                         cli.read_path(path)?;

src/runner.rs

@@ -33,6 +33,22 @@ pub fn get_tty() -> Result<fs::File> {
     }
 }
 
+// In unix system, the std::env::current_dir() calls libc getcwd() that
+// returns physical path. As a workaround, this function tries to use `PWD`
+// environment variable that is configured by shell.
+fn get_current_dir() -> Result<PathBuf, std::io::Error> {
+    let cur = std::env::current_dir();
+    if let Ok(pwd) = std::env::var("PWD") {
+        if pwd.is_empty() {
+            cur
+        } else {
+            Ok(PathBuf::from(pwd))
+        }
+    } else {
+        cur
+    }
+}
+
 fn call_lua_heavy(
     app: &app::App,
     lua: &mlua::Lua,
@@ -110,25 +126,10 @@ pub struct Runner {
     extra_config_files: Vec<PathBuf>,
     on_load: Vec<app::ExternalMsg>,
     read_only: bool,
+    print_pwd_as_result: bool,
     selection: Vec<PathBuf>,
 }
 
-// In unix system, the std::env::current_dir() calls libc getcwd() that
-// returns physical path. As a workaround, this function tries to use `PWD`
-// environment variable that is configured by shell.
-fn get_current_dir() -> Result<PathBuf, std::io::Error> {
-    let cur = std::env::current_dir();
-    if let Ok(pwd) = std::env::var("PWD") {
-        if pwd.is_empty() {
-            cur
-        } else {
-            Ok(PathBuf::from(pwd))
-        }
-    } else {
-        cur
-    }
-}
-
 impl Runner {
     /// Create a new runner object passing the default arguments
     pub fn new() -> Result<Self> {
@@ -161,6 +162,7 @@ impl Runner {
             extra_config_files: cli.extra_config,
             on_load: cli.on_load,
             read_only: cli.read_only,
+            print_pwd_as_result: cli.print_pwd_as_result,
             selection: paths.collect(),
         })
     }
@@ -297,7 +299,12 @@ impl Runner {
                             }
 
                             PrintResultAndQuit => {
-                                result = Ok(Some(app.result_str()));
+                                result = if self.print_pwd_as_result {
+                                    Ok(Some(app.pwd_str()))
+                                } else {
+                                    Ok(Some(app.result_str()))
+                                };
+
                                 break 'outer;
                             }