refactor: rebuild as a column plugin on nemo-repo-core

Keeps only the ColumnProvider from the single file extension; the config, git and cache layers come from nemo-repo-core, so the columns share one git query with the other plugins in the family.

The status string moves to the shared RepoInfo.summary and is now plain ASCII: 2 ahead, 1 behind instead of arrow glyphs. Both columns can be turned off in the config.

nemoRepoColumns.py

@@ -0,0 +1,98 @@
+#!/usr/bin/python3
+"""nemo-repo-columns: "Git Branch" and "Git Status" columns for Nemo.
+
+Enable them per folder through Nemo's own "Visible Columns" dialog, or
+globally under Edit > Preferences > List View. Values are filled in for
+repository roots and left blank everywhere else.
+
+Requires nemo-repo-core: https://github.com/dualfroz/nemo-repo-core
+"""
+
+import importlib.util
+import os
+import sys
+
+
+def _ensureCoreOnPath():
+    if importlib.util.find_spec("nemoRepoCore") is not None:
+        return
+    dataHome = os.environ.get("XDG_DATA_HOME") or os.path.expanduser("~/.local/share")
+    dataDirs = (os.environ.get("XDG_DATA_DIRS") or "/usr/local/share:/usr/share").split(":")
+    for base in [dataHome] + dataDirs:
+        candidate = os.path.join(base, "nemo-repo-core")
+        if os.path.isdir(os.path.join(candidate, "nemoRepoCore")):
+            sys.path.insert(0, candidate)
+            return
+
+
+_ensureCoreOnPath()
+
+import gi
+
+gi.require_version("Nemo", "3.0")
+from gi.repository import GObject, Nemo
+
+from nemoRepoCore import (coreConfig, findRepoRoot, localDirectoryPath,
+                          repoCache, requireCore)
+
+requireCore("1.0.0")
+
+branchAttribute = "repo_branch"
+statusAttribute = "repo_status"
+
+pluginDefaults = {
+    "columns": {
+        "branch": True,
+        "status": True,
+    },
+}
+
+coreConfig.registerDefaults(pluginDefaults)
+
+
+class RepoColumnProvider(GObject.GObject, Nemo.ColumnProvider,
+                         Nemo.InfoProvider, Nemo.NameAndDescProvider):
+
+    def get_columns(self):
+        """Columns are read once, when Nemo loads the extension.
+
+        Turning one off in the config therefore needs a Nemo restart, unlike
+        every other setting in this family.
+        """
+        columns = []
+        if coreConfig.sectionFlag("columns", "branch", True):
+            columns.append(Nemo.Column(name="NemoRepoColumns::branch",
+                                       attribute=branchAttribute,
+                                       label="Git Branch",
+                                       description="Checked out branch of the repository"))
+        if coreConfig.sectionFlag("columns", "status", True):
+            columns.append(Nemo.Column(name="NemoRepoColumns::status",
+                                       attribute=statusAttribute,
+                                       label="Git Status",
+                                       description="Sync state with the upstream plus working tree state"))
+        return columns
+
+    def update_file_info(self, file):
+        path = localDirectoryPath(file)
+        if path is None:
+            return
+
+        repoRoot = findRepoRoot(path)
+        if repoRoot is None:
+            file.add_string_attribute(branchAttribute, "")
+            file.add_string_attribute(statusAttribute, "")
+            return
+
+        repoCache.registerFileObject(repoRoot, file)
+        info = repoCache.get(repoRoot)
+
+        if info.error:
+            file.add_string_attribute(branchAttribute, "?")
+            file.add_string_attribute(statusAttribute, info.error)
+            return
+
+        file.add_string_attribute(branchAttribute, info.branchLabel)
+        file.add_string_attribute(statusAttribute, info.summary)
+
+    def get_name_and_desc(self):
+        return ["nemo-repo-columns:::Git Branch and Git Status columns for the list view"]