feat(fs): add vim.fs.root (#28477)

vim.fs.root() is a function for finding a project root relative to a
buffer using one or more "root markers". This is useful for LSP and
could be useful for other "projects" designs, as well as for any plugins
which work with a "projects" concept.

3 files changed, 35 insertions, 10 deletions

diff --git a/runtime/doc/lsp.txt b/runtime/doc/lsp.txt
index 9385d92416..d1fd84669a 100644
--- a/runtime/doc/lsp.txt
+++ b/runtime/doc/lsp.txt
@@ -34,7 +34,7 @@ Follow these steps to get LSP features:
     vim.lsp.start({
       name = 'my-server-name',
       cmd = {'name-of-language-server-executable'},
-      root_dir = vim.fs.dirname(vim.fs.find({'setup.py', 'pyproject.toml'}, { upward = true })[1]),
+      root_dir = vim.fs.root(0, {'setup.py', 'pyproject.toml'}),
     })
 <
 3. Check that the server attached to the buffer: >
@@ -836,7 +836,7 @@ start({config}, {opts})                                      *vim.lsp.start()*
         vim.lsp.start({
            name = 'my-server-name',
            cmd = {'name-of-language-server-executable'},
-           root_dir = vim.fs.dirname(vim.fs.find({'pyproject.toml', 'setup.py'}, { upward = true })[1]),
+           root_dir = vim.fs.root(0, {'pyproject.toml', 'setup.py'}),
         })
 <
 
@@ -848,7 +848,7 @@ start({config}, {opts})                                      *vim.lsp.start()*
       |vim.lsp.start_client()|.
     • `root_dir` path to the project root. By default this is used to decide
       if an existing client should be re-used. The example above uses
-      |vim.fs.find()| and |vim.fs.dirname()| to detect the root by traversing
+      |vim.fs.root()| and |vim.fs.dirname()| to detect the root by traversing
       the file system upwards starting from the current directory until either
       a `pyproject.toml` or `setup.py` file is found.
     • `workspace_folders` list of `{ uri:string, name: string }` tables
diff --git a/runtime/doc/lua.txt b/runtime/doc/lua.txt
index eaf61ff3fe..92c49bca40 100644
--- a/runtime/doc/lua.txt
+++ b/runtime/doc/lua.txt
@@ -2891,13 +2891,6 @@ vim.fs.find({names}, {opts})                                   *vim.fs.find()*
     narrow the search to find only that type.
 
     Examples: >lua
-        -- location of Cargo.toml from the current buffer's path
-        local cargo = vim.fs.find('Cargo.toml', {
-          upward = true,
-          stop = vim.uv.os_homedir(),
-          path = vim.fs.dirname(vim.api.nvim_buf_get_name(0)),
-        })
-
         -- list all test directories under the runtime directory
         local test_dirs = vim.fs.find(
           {'test', 'tst', 'testdir'},
@@ -3013,6 +3006,35 @@ vim.fs.parents({start})                                     *vim.fs.parents()*
         (`nil`)
         (`string?`)
 
+vim.fs.root({source}, {marker})                                *vim.fs.root()*
+    Find the first parent directory containing a specific "marker", relative
+    to a buffer's directory.
+
+    Example: >lua
+        -- Find the root of a Python project, starting from file 'main.py'
+        vim.fs.root(vim.fs.joinpath(vim.env.PWD, 'main.py'), {'pyproject.toml', 'setup.py' })
+
+        -- Find the root of a git repository
+        vim.fs.root(0, '.git')
+
+        -- Find the parent directory containing any file with a .csproj extension
+        vim.fs.root(0, function(name, path)
+          return name:match('%.csproj$') ~= nil
+        end)
+<
+
+    Parameters: ~
+      • {source}  (`integer|string`) Buffer number (0 for current buffer) or
+                  file path to begin the search from.
+      • {marker}  (`string|string[]|fun(name: string, path: string): boolean`)
+                  A marker, or list of markers, to search for. If a function,
+                  the function is called for each evaluated item and should
+                  return true if {name} and {path} are a match.
+
+    Return: ~
+        (`string?`) Directory path containing one of the given markers, or nil
+        if no directory was found.
+
 
 ==============================================================================
 Lua module: vim.glob                                                *vim.glob*
diff --git a/runtime/doc/news.txt b/runtime/doc/news.txt
index 5e2a48701e..c05e060920 100644
--- a/runtime/doc/news.txt
+++ b/runtime/doc/news.txt
@@ -365,6 +365,9 @@ The following new APIs and features were added.
 
 • Added built-in |commenting| support.
 
+• |vim.fs.root()| finds project root directories from a list of "root
+  markers".
+
 ==============================================================================
 CHANGED FEATURES                                                 *news-changed*