If a name isn't provided, try to infer it from the git repo (#202)

* Added assert_not_defined check

* Function to get package name form git uri and tests

* Autofix format

* If name is not provided, try to infer it from the git repo

* Unset result of cpm_package_name_from_git_uri if there is no match
- Also reordered tests to ensure that the result is actually unset when needed

* Removed trailing spaces in README

* Updated the main example with the new minimal syntax

* Well... autofix format again

* Update error message for missing name to reflect the possible auto-infer step

* Autofix format... yet again :)

test/unit/package_name_from_git_uri.cmake

@@ -0,0 +1,28 @@
+cmake_minimum_required(VERSION 3.14 FATAL_ERROR)
+
+include(${CPM_PATH}/CPM.cmake)
+include(${CPM_PATH}/testing.cmake)
+
+cpm_package_name_from_git_uri("https://github.com/cpm-cmake/CPM.cmake.git" name)
+assert_equal("CPM.cmake" ${name})
+
+cpm_package_name_from_git_uri("ssh://user@host.xz:123/path/to/pkg.git/" name)
+assert_equal("pkg" ${name})
+
+cpm_package_name_from_git_uri("git://host.xz/path/to/pkg.git" name)
+assert_equal("pkg" ${name})
+
+cpm_package_name_from_git_uri("git@host.xz:cool-pkg.git" name)
+assert_equal("cool-pkg" ${name})
+
+cpm_package_name_from_git_uri("file:///path/to/pkg33.git" name)
+assert_equal("pkg33" ${name})
+
+cpm_package_name_from_git_uri("../local-repo/.git" name)
+assert_equal("local-repo" ${name})
+
+cpm_package_name_from_git_uri("asdf" name)
+assert_not_defined(name)
+
+cpm_package_name_from_git_uri("/something.git/stuff" name)
+assert_not_defined(name)