Add relative path support to Git SCM tool (#11407)

* Let Git SCM support relative paths

* Update conans/test/unittests/tools/scm/test_git_get_commit.py

Add test for relative folder paths

* Update conans/test/unittests/tools/scm/test_git_get_commit.py

- Test that submodules work as subfolders

conan/tools/scm/git.py

@@ -22,7 +22,7 @@ def get_commit(self):
             # --full-history is needed to not avoid wrong commits:
             # https://github.com/conan-io/conan/issues/10971
             # https://git-scm.com/docs/git-rev-list#Documentation/git-rev-list.txt-Defaultmode
-            commit = self._run('rev-list HEAD -n 1 --full-history -- "{}"'.format(self.folder))
+            commit = self._run('rev-list HEAD -n 1 --full-history -- "."')
             return commit
         except Exception as e:
             raise ConanException("Unable to get git commit in '%s': %s" % (self.folder, str(e)))

conans/test/unittests/tools/scm/test_git_get_commit.py

@@ -1,6 +1,7 @@
 import os
 
 from conan.tools.scm import Git
+from conans.tools import chdir
 from conans.test.utils.mocks import MockConanfile
 from conans.test.utils.tools import TestClient
 
@@ -97,3 +98,109 @@ def test_multi_folder_repo():
     c.run_command("git rev-parse HEAD")
     commit_real = str(c.out).splitlines()[0]
     assert new_commit_root == commit_real
+
+def test_relative_folder_repo():
+    c = TestClient()
+    conanfile = MockConanfile({})
+    c.save({"lib_a/conanfile.py": ""})
+    c.run_command("git init .")
+    c.run_command('git config user.name myname')
+    c.run_command('git config user.email myname@mycompany.com')
+    c.run_command("git add .")
+    c.run_command('git commit -m "lib_a commit"')
+    c.save({"lib_b/conanfile.py": ""})
+    c.run_command("git add .")
+    c.run_command('git commit -m "lib_b commit"')
+    c.save({"lib_c/conanfile.py": ""})
+    c.run_command("git add .")
+    c.run_command('git commit -m "lib_c commit"')
+    c.save({"root_change": ""})
+    c.run_command("git add .")
+    c.run_command('git commit -m "root change"')
+
+    # Relative paths for folders, from the current_folder
+    with chdir(c.current_folder):
+        git = Git(conanfile, folder="lib_a")
+        commit_libA = git.get_commit()
+
+        git = Git(conanfile, folder="lib_b")
+        commit_libB = git.get_commit()
+
+        git = Git(conanfile, folder="./lib_c")
+        commit_libC = git.get_commit()
+
+        # this is folder default, but be explicit
+        git = Git(conanfile, folder=".")
+        commit_root = git.get_commit()
+
+    # All different
+    assert len({commit_libA, commit_libB, commit_libC, commit_root}) == 4
+
+    # Compare to Full paths
+    git = Git(conanfile, folder=os.path.join(c.current_folder, "lib_a"))
+    full_commit_libA = git.get_commit()
+
+    git = Git(conanfile, folder=os.path.join(c.current_folder, "lib_b"))
+    full_commit_libB = git.get_commit()
+
+    git = Git(conanfile, folder=os.path.join(c.current_folder, "lib_c"))
+    full_commit_libC = git.get_commit()
+
+    git = Git(conanfile, folder=c.current_folder)
+    full_commit_root = git.get_commit()
+
+    assert full_commit_libA == commit_libA
+    assert full_commit_libB == commit_libB
+    assert full_commit_libC == commit_libC
+    assert full_commit_root == commit_root
+
+    # Sanity checks
+    c.run_command("git rev-parse HEAD")
+    commit_real_root = str(c.out).splitlines()[0]
+    assert commit_real_root == commit_root
+
+    c.run_command("git rev-list -n 1 --full-history HEAD -- lib_a")
+    commit_real_libA = str(c.out).splitlines()[0]
+    assert commit_real_libA == commit_libA
+
+def test_submodule_repo():
+    c = TestClient()
+    conanfile = MockConanfile({})
+    c.save({"conanfile.py": ""})
+    c.run_command("git init .")
+    c.run_command('git config user.name myname')
+    c.run_command('git config user.email myname@mycompany.com')
+    c.run_command("git add .")
+    c.run_command('git commit -m "Initial commit"')
+    c.run_command('git clone . source_subfolder')
+    c.run_command('git submodule add ../ source_subfolder')
+    c.run_command('git commit -m "submodule commit"')
+    c.save({"root_change": ""})
+    c.run_command("git add .")
+    c.run_command('git commit -m "root change"')
+
+    with chdir(c.current_folder):
+        # default case
+        git = Git(conanfile)
+        commit_root = git.get_commit()
+
+        # Relative paths
+        git = Git(conanfile, folder="source_subfolder")
+        commit_relA = git.get_commit()
+
+        git = Git(conanfile, folder="./source_subfolder")
+        commit_relB = git.get_commit()
+
+        # Full path
+        git = Git(conanfile, folder=os.path.join(c.current_folder, "source_subfolder"))
+        commit_full = git.get_commit()
+
+    assert commit_relA == commit_relB
+    assert commit_relA == commit_full
+    assert commit_root != commit_full
+
+    # This is the commit which modified the tree in the containing repo
+    # not the commit which the submodule is at
+    c.run_command("git rev-list HEAD -n 1 --full-history -- source_subfolder")
+    commit_submodule = str(c.out).splitlines()[0]
+    assert commit_submodule != commit_full