introducing modern conan.tool.scm.Git helper

conan/tools/files/files.py

@@ -4,6 +4,7 @@
 import hashlib
 import os
 import platform
+import shutil
 import subprocess
 import sys
 from contextlib import contextmanager
@@ -14,6 +15,7 @@
 from conan.tools import CONAN_TOOLCHAIN_ARGS_FILE, CONAN_TOOLCHAIN_ARGS_SECTION
 from conans.client.downloaders.download import run_downloader
 from conans.errors import ConanException
+from conans.util.files import rmdir
 
 if six.PY3:  # Remove this IF in develop2
     from shutil import which
@@ -491,3 +493,20 @@ def collect_libs(conanfile, folder=None):
                     result.append(name)
     result.sort()
     return result
+
+
+def swap_child_folder(parent_folder, child_folder):
+    """ replaces the current folder contents with the contents of one child folder. This
+    is used in the SCM monorepo flow, when it is necessary to use one subproject subfolder
+    to replace the whole cloned git repo
+    """
+    for f in os.listdir(parent_folder):
+        if f != child_folder:
+            path = os.path.join(parent_folder, f)
+            if os.path.isfile(path):
+                os.remove(path)
+            else:
+                rmdir(path)
+    child = os.path.join(parent_folder, child_folder)
+    for f in os.listdir(child):
+        shutil.move(os.path.join(child, f), os.path.join(parent_folder, f))

conan/tools/scm/__init__.py

@@ -0,0 +1 @@
+from conan.tools.scm.git import Git

conan/tools/scm/git.py

@@ -0,0 +1,85 @@
+import os
+
+from conan.tools.files import chdir
+from conans.errors import ConanException
+from conans.util.files import mkdir
+from conans.util.runners import check_output_runner
+
+
+class Git(object):
+    def __init__(self, conanfile, folder="."):
+        self._conanfile = conanfile
+        self.folder = folder
+
+    def _run(self, cmd):
+        with chdir(self._conanfile, self.folder):
+            return check_output_runner("git {}".format(cmd)).strip()
+
+    def get_commit(self):
+        try:
+            # commit = self._run("rev-parse HEAD") For the whole repo
+            # This rev-list knows to capture the last commit for the folder
+            commit = self._run('rev-list HEAD -n 1 -- "{}"'.format(self.folder))
+            return commit
+        except Exception as e:
+            raise ConanException("Unable to get git commit in '%s': %s" % (self.folder, str(e)))
+
+    def get_remote_url(self, remote="origin"):
+        remotes = self._run("remote -v")
+        for r in remotes.splitlines():
+            name, url = r.split(maxsplit=1)
+            if name == remote:
+                url, _ = url.rsplit(None, 1)
+                if os.path.exists(url):  # Windows local directory
+                    url = url.replace("\\", "/")
+                return url
+
+    def commit_in_remote(self, commit, remote="origin"):
+        if not remote:
+            return False
+        try:
+            branches = self._run("branch -r --contains {}".format(commit))
+            return "{}/".format(remote) in branches
+        except Exception as e:
+            raise ConanException("Unable to check remote commit in '%s': %s" % (self.folder, str(e)))
+
+    def is_dirty(self):
+        status = self._run("status -s").strip()
+        return bool(status)
+
+    def get_url_and_commit(self, remote="origin"):
+        dirty = self.is_dirty()
+        if dirty:
+            raise ConanException("Repo is dirty, cannot capture url and commit: "
+                                 "{}".format(self.folder))
+        commit = self.get_commit()
+        url = self.get_remote_url(remote=remote)
+        in_remote = self.commit_in_remote(commit, remote=remote)
+        if in_remote:
+            return url, commit
+        # TODO: Once we know how to pass [conf] to export, enable this
+        # conf_name = "tools.scm:local"
+        # allow_local = self._conanfile.conf[conf_name]
+        # if not allow_local:
+        #    raise ConanException("Current commit {} doesn't exist in remote {}\n"
+        #                         "use '-c {}=1' to allow it".format(commit, remote, conf_name))
+
+        self._conanfile.output.warn("Current commit {} doesn't exist in remote {}\n"
+                                    "This revision will not be buildable in other "
+                                    "computer".format(commit, remote))
+        return self.get_repo_root(), commit
+
+    def get_repo_root(self):
+        folder = self._run("rev-parse --show-toplevel")
+        return folder.replace("\\", "/")
+
+    def clone(self, url, target=""):
+        if os.path.exists(url):
+            url = url.replace("\\", "/")  # Windows local directory
+        mkdir(self.folder)
+        self._conanfile.output.info("Cloning git repo")
+        self._run('clone "{}" {}'.format(url, target))
+
+    def checkout(self, commit):
+        self._conanfile.output.info("Checkout: {}".format(commit))
+        self._run('checkout {}'.format(commit))