Fix recent git commands to work back on 2.7.4.

include/vcpkg/base/files.h

@@ -213,6 +213,7 @@ namespace vcpkg
 
         virtual Path absolute(const Path& target, std::error_code& ec) const = 0;
         Path absolute(const Path& target, LineInfo li) const;
+        Optional<Path> absolute(DiagnosticContext& context, const Path& target) const;
 
         virtual std::vector<Path> find_from_PATH(View<StringView> stems) const = 0;
         std::vector<Path> find_from_PATH(StringView stem) const;

include/vcpkg/base/git.h

@@ -56,7 +56,15 @@ namespace vcpkg
 
     Optional<std::string> git_prefix(DiagnosticContext& context, const Path& git_exe, const Path& target);
 
-    Optional<Path> git_index_file(DiagnosticContext& context, const Path& git_exe, GitRepoLocator locator);
+    Optional<Path> git_index_file(DiagnosticContext& context,
+                                  const Filesystem& fs,
+                                  const Path& git_exe,
+                                  GitRepoLocator locator);
+
+    Optional<Path> git_absolute_git_dir(DiagnosticContext& context,
+                                        const Filesystem& fs,
+                                        const Path& git_exe,
+                                        GitRepoLocator locator);
 
     bool git_add_with_index(DiagnosticContext& context,
                             const Path& git_exe,

src/vcpkg/base/files.cpp

@@ -1893,6 +1893,19 @@ namespace vcpkg
         return result;
     }
 
+    Optional<Path> ReadOnlyFilesystem::absolute(DiagnosticContext& context, const Path& target) const
+    {
+        std::error_code ec;
+        Optional<Path> result{this->absolute(target, ec)};
+        if (ec)
+        {
+            context.report_error(format_filesystem_call_error(ec, __func__, {target}));
+            result.clear();
+        }
+
+        return result;
+    }
+
     std::vector<Path> ReadOnlyFilesystem::find_from_PATH(StringView stem) const
     {
         return this->find_from_PATH(View<StringView>{&stem, 1});
@@ -2052,11 +2065,11 @@ namespace vcpkg
                                                 const Path& new_path) const
     {
         std::error_code ec;
-        bool result = this->rename_or_delete(old_path, new_path, ec);
+        Optional<bool> result{this->rename_or_delete(old_path, new_path, ec)};
         if (ec)
         {
             context.report_error(format_filesystem_call_error(ec, __func__, {old_path, new_path}));
-            return nullopt;
+            result.clear();
         }
 
         return result;
@@ -2089,11 +2102,11 @@ namespace vcpkg
     Optional<bool> Filesystem::create_directory(DiagnosticContext& context, const Path& new_directory) const
     {
         std::error_code ec;
-        bool result = this->create_directory(new_directory, ec);
+        Optional<bool> result{this->create_directory(new_directory, ec)};
         if (ec)
         {
             context.report_error(format_filesystem_call_error(ec, __func__, {new_directory}));
-            return nullopt;
+            result.clear();
         }
 
         return result;
@@ -2114,11 +2127,11 @@ namespace vcpkg
     Optional<bool> Filesystem::create_directories(DiagnosticContext& context, const Path& new_directory) const
     {
         std::error_code ec;
-        bool result = this->create_directories(new_directory, ec);
+        Optional<bool> result{this->create_directories(new_directory, ec)};
         if (ec)
         {
             context.report_error(format_filesystem_call_error(ec, __func__, {new_directory}));
-            return nullopt;
+            result.clear();
         }
 
         return result;
@@ -2213,11 +2226,11 @@ namespace vcpkg
                                          CopyOptions options) const
     {
         std::error_code ec;
-        const bool result = this->copy_file(source, destination, options, ec);
+        Optional<bool> result{this->copy_file(source, destination, options, ec)};
         if (ec)
         {
             context.report_error(format_filesystem_call_error(ec, __func__, {source, destination}));
-            return nullopt;
+            result.clear();
         }
 
         return result;

src/vcpkg/base/git.cpp

@@ -12,6 +12,14 @@
 
 #include <algorithm>
 
+// When making changes to this file, check that the git command lines intended do what is expected on
+// vcpkg's current minimum supported git version (2.7.4). You can get a version of git that old with docker:
+//
+// docker run -it --rm ubuntu:16.04
+// apt update
+// apt install git
+// git --version # check that this is 2.7.4
+
 namespace
 {
     using namespace vcpkg;
@@ -114,6 +122,8 @@ namespace vcpkg
 
     Optional<bool> is_shallow_clone(DiagnosticContext& context, const Path& git_exe, GitRepoLocator locator)
     {
+        // --is-shallow-repository is not present in git 2.7.4, but in that case git just prints
+        // "--is-shallow-repository", which is not "true", so we safely report "false"
         static constexpr StringView args[] = {StringLiteral{"rev-parse"}, StringLiteral{"--is-shallow-repository"}};
         return run_cmd_trim(context, make_git_command(git_exe, locator, args)).map([](std::string&& output) {
             return output == "true";
@@ -127,14 +137,48 @@ namespace vcpkg
             context, make_git_command(git_exe, GitRepoLocator{GitRepoLocatorKind::CurrentDirectory, target}, args));
     }
 
-    Optional<Path> git_index_file(DiagnosticContext& context, const Path& git_exe, GitRepoLocator locator)
+    Optional<Path> git_index_file(DiagnosticContext& context,
+                                  const Filesystem& fs,
+                                  const Path& git_exe,
+                                  GitRepoLocator locator)
+    {
+        // We can't use --path-format unconditionally as that is unavailable in git 2.7.4.
+        // However, the path format always appears to be absolute if we use --git-dir with an absolute path
+        static constexpr StringView args[] = {
+            StringLiteral{"rev-parse"}, StringLiteral{"--git-path"}, StringLiteral{"index"}};
+        return git_absolute_git_dir(context, fs, git_exe, locator).then([&](Path&& absolute_git_dir) {
+            auto git_path_index_cmd =
+                make_git_command(git_exe, GitRepoLocator{GitRepoLocatorKind::DotGitDir, absolute_git_dir}, args);
+            return run_cmd_trim(context, git_path_index_cmd).then([&](std::string&& proto_path) -> Optional<Path> {
+                Optional<Path> result;
+                auto& result_path = result.emplace(std::move(proto_path));
+                if (!result_path.is_absolute() || !fs.exists(result_path, IgnoreErrors{}))
+                {
+                    context.report_error_with_log(result_path.native(),
+                                                  msgGitUnexpectedCommandOutputCmd,
+                                                  msg::command_line = git_path_index_cmd.command_line());
+                    result.clear();
+                }
+
+                return result;
+            });
+        });
+    }
+
+    Optional<Path> git_absolute_git_dir(DiagnosticContext& context,
+                                        const Filesystem& fs,
+                                        const Path& git_exe,
+                                        GitRepoLocator locator)
     {
-        static constexpr StringView args[] = {StringLiteral{"rev-parse"},
-                                              StringLiteral{"--path-format=absolute"},
-                                              StringLiteral{"--git-path"},
-                                              StringLiteral{"index"}};
-        return run_cmd_trim(context, make_git_command(git_exe, locator, args))
-            .map([](std::string&& proto_path) -> Path { return std::move(proto_path); });
+        static constexpr StringView args[] = {StringLiteral{"rev-parse"}, StringLiteral{"--git-dir"}};
+        switch (locator.kind)
+        {
+            case GitRepoLocatorKind::CurrentDirectory:
+                return run_cmd_trim(context, make_git_command(git_exe, locator, args))
+                    .then([&](std::string&& proto_path) { return fs.absolute(context, locator.path / proto_path); });
+            case GitRepoLocatorKind::DotGitDir: return fs.absolute(context, locator.path);
+            default: Checks::unreachable(VCPKG_LINE_INFO);
+        }
     }
 
     bool git_add_with_index(DiagnosticContext& context, const Path& git_exe, const Path& target, const Path& index_file)
@@ -197,6 +241,7 @@ namespace vcpkg
         RedirectedProcessLaunchSettings launch_settings;
         launch_settings.encoding = Encoding::Utf8WithNulls;
         Optional<std::vector<GitLSTreeEntry>> result;
+
         StringView args[] = {StringLiteral{"ls-tree"}, treeish, StringLiteral{"--full-tree"}, StringLiteral{"-z"}};
         auto cmd = make_git_command(git_exe, locator, args);
         auto maybe_ls_tree_result = run_cmd_trim(context, cmd, launch_settings);
@@ -242,12 +287,12 @@ namespace vcpkg
         auto read_tree_cmd = make_git_command(git_exe, locator, read_tree_args);
         if (run_cmd_git_with_index(context, read_tree_cmd, git_tree_index).has_value())
         {
+            // No --ignore-skip-worktree-bits because that was added in recent-ish git versions
             auto prefix_arg = fmt::format("--prefix={}/", git_tree_temp);
             StringView checkout_index_args[] = {StringLiteral{"--work-tree"},
                                                 git_tree_temp,
                                                 StringLiteral{"checkout-index"},
                                                 StringLiteral{"-af"},
-                                                StringLiteral{"--ignore-skip-worktree-bits"},
                                                 prefix_arg};
             auto checkout_index_cmd = make_git_command(git_exe, locator, checkout_index_args);
             bool succeeded = run_cmd_git_with_index(context, checkout_index_cmd, git_tree_index).has_value();

src/vcpkg/commands.test-features.cpp

@@ -63,7 +63,7 @@ namespace
             git_prefix(console_diagnostic_context, git_exe, builtin_ports).value_or_quiet_exit(VCPKG_LINE_INFO);
         const auto locator = GitRepoLocator{GitRepoLocatorKind::CurrentDirectory, builtin_ports};
         auto index_file =
-            git_index_file(console_diagnostic_context, git_exe, locator).value_or_quiet_exit(VCPKG_LINE_INFO);
+            git_index_file(console_diagnostic_context, fs, git_exe, locator).value_or_quiet_exit(VCPKG_LINE_INFO);
         TempFileDeleter temp_index_file{fs, fmt::format("{}_vcpkg_{}.tmp", index_file.native(), get_process_id())};
         if (!fs.copy_file(
                 console_diagnostic_context, index_file, temp_index_file.path, CopyOptions::overwrite_existing) ||

src/vcpkg/vcpkgpaths.cpp

@@ -1005,7 +1005,7 @@ namespace vcpkg
         if (auto prefix = maybe_prefix.get())
         {
             const auto locator = GitRepoLocator{GitRepoLocatorKind::CurrentDirectory, builtin_ports};
-            const auto maybe_index_file = git_index_file(context, git_exe, locator);
+            const auto maybe_index_file = git_index_file(context, fs, git_exe, locator);
             if (const auto index_file = maybe_index_file.get())
             {
                 TempFileDeleter temp_index_file{fs,