add option to require explicit fetch/checkout

dvc/output.py

@@ -88,6 +88,7 @@ def loadd_from(stage, d_list):
     for d in d_list:
         p = d.pop(Output.PARAM_PATH)
         cache = d.pop(Output.PARAM_CACHE, True)
+        explicit = d.pop(Output.PARAM_EXPLICIT, False)
         metric = d.pop(Output.PARAM_METRIC, False)
         plot = d.pop(Output.PARAM_PLOT, False)
         persist = d.pop(Output.PARAM_PERSIST, False)
@@ -103,6 +104,7 @@ def loadd_from(stage, d_list):
                 p,
                 info=d,
                 cache=cache,
+                explicit=explicit,
                 metric=metric,
                 plot=plot,
                 persist=persist,
@@ -282,6 +284,7 @@ class Output:
 
     PARAM_PATH = "path"
     PARAM_CACHE = "cache"
+    PARAM_EXPLICIT = "explicit"
     PARAM_FILES = "files"
     PARAM_METRIC = "metric"
     PARAM_METRIC_TYPE = "type"
@@ -312,6 +315,7 @@ def __init__(  # noqa: PLR0913
         path,
         info=None,
         cache=True,
+        explicit=False,
         metric=False,
         plot=False,
         persist=False,
@@ -384,6 +388,7 @@ def __init__(  # noqa: PLR0913
             files = [merge_file_meta_from_cloud(f) for f in files]
         self.files = files
         self.use_cache = False if self.IS_DEPENDENCY else cache
+        self.explicit = explicit
         self.metric = False if self.IS_DEPENDENCY else metric
         self.plot = False if self.IS_DEPENDENCY else plot
         self.persist = persist
@@ -1500,6 +1505,7 @@ def _merge_dir_version_meta(self, other: "Output"):
     **ARTIFACT_SCHEMA,
     **ANNOTATION_SCHEMA,
     Output.PARAM_CACHE: bool,
+    Output.PARAM_EXPLICIT: bool,
     Output.PARAM_REMOTE: str,
     Output.PARAM_PUSH: bool,
     Output.PARAM_FILES: [DIR_FILES_SCHEMA],

dvc/repo/checkout.py

@@ -127,8 +127,13 @@ def onerror(target, exc):
             raise CheckoutErrorSuggestGit(target) from exc
         raise
 
+    def outs_filter(out: "Output") -> bool:
+        if out.explicit and not [t for t in targets if t]:
+            return False
+        return True
+
     view = self.index.targets_view(
-        targets, recursive=recursive, with_deps=with_deps, onerror=onerror
+        targets, recursive=recursive, with_deps=with_deps, onerror=onerror, outs_filter=outs_filter
     )
 
     with ui.progress(unit="entry", desc="Building workspace index", leave=True) as pb:

dvc/repo/fetch.py

@@ -55,6 +55,8 @@ def stage_filter(stage: "Stage") -> bool:
     def outs_filter(out: "Output") -> bool:
         if push and not out.can_push:
             return False
+        if out.explicit and not [t for t in targets if t]:
+            return False
         return not (remote and out.remote and remote != out.remote)
 
     for rev in repo.brancher(