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 :)

README.md

@@ -43,7 +43,7 @@ CPMAddPackage(
 
 The origin may be specified by a `GIT_REPOSITORY`, but other sources, such as direct URLs, are [also supported](https://cmake.org/cmake/help/v3.11/module/ExternalProject.html#external-project-definition).
 If `GIT_TAG` hasn't been explicitly specified it defaults to `v(VERSION)`, a common convention for git projects.
-On the other hand, if `VERSION` hasn't been explicitly specified, CPM can automatically identify the version from the git tag in some common cases. 
+On the other hand, if `VERSION` hasn't been explicitly specified, CPM can automatically identify the version from the git tag in some common cases.
 `GIT_TAG` can also be set to a specific commit or a branch name such as `master` to always download the most recent version.
 The optional argument `FIND_PACKAGE_ARGUMENTS` can be specified to a string of parameters that will be passed to `find_package` if enabled (see below).
 
@@ -71,7 +71,6 @@ add_executable(tests tests.cpp)
 include(cmake/CPM.cmake)
 
 CPMAddPackage(
-  NAME Catch2
   GITHUB_REPOSITORY catchorg/Catch2
   VERSION 2.5.0
 )
@@ -112,7 +111,7 @@ Dependencies using CPM will automatically use the updated script of the outermos
 ## Limitations
 
 - **No pre-built binaries** For every new build directory, all dependencies are initially downloaded and built from scratch. To avoid extra downloads it is recommend to set the [`CPM_SOURCE_CACHE`](#CPM_SOURCE_CACHE) environmental variable. Using a caching compiler such as [ccache](https://github.com/TheLartians/Ccache.cmake) can drastically reduce build time.
-- **Dependent on good CMakeLists** Many libraries do not have CMakeLists that work well for subprojects. Luckily this is slowly changing, however, until then, some manual configuration may be required (see the snippets [below](#snippets) for examples). For best practices on preparing projects for CPM, see the [wiki](https://github.com/cpm-cmake/CPM.cmake/wiki/Preparing-projects-for-CPM.cmake). 
+- **Dependent on good CMakeLists** Many libraries do not have CMakeLists that work well for subprojects. Luckily this is slowly changing, however, until then, some manual configuration may be required (see the snippets [below](#snippets) for examples). For best practices on preparing projects for CPM, see the [wiki](https://github.com/cpm-cmake/CPM.cmake/wiki/Preparing-projects-for-CPM.cmake).
 - **First version used** In diamond-shaped dependency graphs (e.g. `A` depends on `C`@1.1 and `B`, which itself depends on `C`@1.2 the first added dependency will be used (in this case `C`@1.1). In this case, B requires a newer version of `C` than `A`, so CPM will emit a warning. This can be easily resolved by adding a new version of the dependency in the outermost project, or by introducing a [package lock file](#package-lock).
 
 For projects with more complex needs and where an extra setup step doesn't matter, it may be worth to check out an external C++ package manager such as [vcpkg](https://github.com/microsoft/vcpkg), [conan](https://conan.io) or [hunter](https://github.com/ruslo/hunter).
@@ -143,7 +142,7 @@ The most notable features are:
 - [Package lock files](#package-lock) for easier transitive dependency management.
 - Dependencies can be overridden [per-build](#local-package-override) using CMake CLI parameters.
 
-ExternalProject works similarly as FetchContent, however waits with adding dependencies until build time. 
+ExternalProject works similarly as FetchContent, however waits with adding dependencies until build time.
 This has a quite a few disadvantages, especially as it makes using custom toolchains / cross-compiling very difficult and can lead to problems with nested dependencies.
 
 ## Options
@@ -178,7 +177,7 @@ These options can also be set as environmental variables.
 
 Library developers are often in the situation where they work on a locally checked out dependency at the same time as on a consumer project.
 It is possible to override the consumer's dependency with the version by supplying the CMake option `CPM_<dependency name>_SOURCE` set to the absolute path of the local library.
-For example, to use the local version of the dependency `Dep` at the path `/path/to/dep`, the consumer can be built with the following command. 
+For example, to use the local version of the dependency `Dep` at the path `/path/to/dep`, the consumer can be built with the following command.
 
 ```bash
 cmake -Bbuild -DCPM_Dep_SOURCE=/path/to/dep
@@ -205,7 +204,7 @@ See the [wiki](https://github.com/cpm-cmake/CPM.cmake/wiki/Package-lock) for mor
 
 ## Built with CPM.cmake
 
-Some amazing projects that are built using the CPM.cmake package manager. 
+Some amazing projects that are built using the CPM.cmake package manager.
 If you know others, feel free to add them here through a PR.
 
 <table>
@@ -284,7 +283,7 @@ CPMAddPackage(
   # 0.6.2 uses deprecated CMake syntax
   VERSION 0.6.3
   # 0.6.3 is not released yet, so use a recent commit
-  GIT_TAG 012269756149ae99745b6dafefd415843d7420bb 
+  GIT_TAG 012269756149ae99745b6dafefd415843d7420bb
   OPTIONS
     "YAML_CPP_BUILD_TESTS Off"
     "YAML_CPP_BUILD_CONTRIB Off"
@@ -314,7 +313,7 @@ endif()
 ```cmake
 CPMAddPackage(
   NAME nlohmann_json
-  VERSION 3.6.1  
+  VERSION 3.6.1
   # the git repo is incredibly large, so we download the archived include directory
   URL https://github.com/nlohmann/json/releases/download/v3.6.1/include.zip
   URL_HASH SHA256=69cc88207ce91347ea530b227ff0776db82dcb8de6704e1a3d74f4841bc651cf
@@ -337,7 +336,7 @@ CPMAddPackage(
   DOWNLOAD_ONLY True
 )
 
-if(range-v3_ADDED) 
+if(range-v3_ADDED)
   add_library(range-v3 INTERFACE IMPORTED)
   target_include_directories(range-v3 INTERFACE "${range-v3_SOURCE_DIR}/include")
 endif()

cmake/CPM.cmake

@@ -134,6 +134,19 @@ endif()
 include(FetchContent)
 include(CMakeParseArguments)
 
+# Infer package name from git repository uri (path or url)
+function(cpm_package_name_from_git_uri URI RESULT)
+  string(REGEX MATCH "([^/:]+)/?.git/?$" cpmGitUriMatch "${URI}")
+  if(DEFINED cpmGitUriMatch)
+    set(${RESULT}
+        ${CMAKE_MATCH_1}
+        PARENT_SCOPE
+    )
+  else()
+    unset(${RESULT} PARENT_SCOPE)
+  endif()
+endfunction()
+
 # Initialize logging prefix
 if(NOT CPM_INDENT)
   set(CPM_INDENT
@@ -264,12 +277,6 @@ function(CPMAddPackage)
 
   cmake_parse_arguments(CPM_ARGS "" "${oneValueArgs}" "${multiValueArgs}" "${ARGN}")
 
-  # Check for required arguments
-
-  if(NOT DEFINED CPM_ARGS_NAME)
-    message(FATAL_ERROR "CPM: 'NAME' was not provided for package added with arguments: '${ARGN}'")
-  endif()
-
   # Set default values for arguments
 
   if(NOT DEFINED CPM_ARGS_VERSION)
@@ -297,6 +304,11 @@ function(CPMAddPackage)
     if(NOT DEFINED CPM_ARGS_GIT_TAG)
       set(CPM_ARGS_GIT_TAG v${CPM_ARGS_VERSION})
     endif()
+
+    # If a name wasn't provided, try to infer it from the git repo
+    if(NOT DEFINED CPM_ARGS_NAME)
+      cpm_package_name_from_git_uri(${CPM_ARGS_GIT_REPOSITORY} CPM_ARGS_NAME)
+    endif()
   endif()
 
   set(CPM_SKIP_FETCH FALSE)
@@ -309,6 +321,15 @@ function(CPMAddPackage)
     endif()
   endif()
 
+  # Check for required arguments
+
+  if(NOT DEFINED CPM_ARGS_NAME)
+    message(
+      FATAL_ERROR
+        "CPM: 'NAME' was not provided and couldn't be automatically inferred for package added with arguments: '${ARGN}'"
+    )
+  endif()
+
   # Check if package has been added before
   cpm_check_if_package_already_added(${CPM_ARGS_NAME} "${CPM_ARGS_VERSION}" "${CPM_ARGS_OPTIONS}")
   if(CPM_PACKAGE_ALREADY_ADDED)

cmake/testing.cmake

@@ -36,6 +36,14 @@ function(ASSERT_DEFINED KEY)
   endif()
 endfunction()
 
+function(ASSERT_NOT_DEFINED KEY)
+  if(DEFINED ${KEY})
+    message(FATAL_ERROR "assertion failed: '${KEY}' is defiend")
+  else()
+    message(STATUS "test passed: '${KEY}' is not defined")
+  endif()
+endfunction()
+
 function(ASSERT_TRUTHY KEY)
   if(${${KEY}})
     message(STATUS "test passed: '${KEY}' is set truthy")

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)