tap: add methods to get git related information

These methods will be used in `brew --version`, `brew config`
and `brew doctor` after core/formula separation.

Closes Homebrew/homebrew#49796.

Signed-off-by: Xu Cheng <xucheng@me.com>

1 files changed, 29 insertions, 1 deletions

diff --git a/Library/Homebrew/tap.rb b/Library/Homebrew/tap.rb
index 8519a3c6d..8958e3b11 100644
--- a/Library/Homebrew/tap.rb
+++ b/Library/Homebrew/tap.rb
@@ -83,7 +83,7 @@ class Tap
   # e.g. `https://github.com/user/homebrew-repo`
   def remote
     @remote ||= if installed?
-      if git?
+      if git? && Utils.git_available?
         path.cd do
           Utils.popen_read("git", "config", "--get", "remote.origin.url").chomp
         end
@@ -98,6 +98,34 @@ class Tap
     (path/".git").exist?
   end
 
+  # git HEAD for this {Tap}.
+  def git_head
+    raise TapUnavailableError, name unless installed?
+    return unless git? && Utils.git_available?
+    path.cd { Utils.popen_read("git", "rev-parse", "--verify", "-q", "HEAD").chuzzle }
+  end
+
+  # git HEAD in short format for this {Tap}.
+  def git_short_head
+    raise TapUnavailableError, name unless installed?
+    return unless git? && Utils.git_available?
+    path.cd { Utils.popen_read("git", "rev-parse", "--short=4", "--verify", "-q", "HEAD").chuzzle }
+  end
+
+  # time since git last commit for this {Tap}.
+  def git_last_commit
+    raise TapUnavailableError, name unless installed?
+    return unless git? && Utils.git_available?
+    path.cd { Utils.popen_read("git", "show", "-s", "--format=%cr", "HEAD").chuzzle }
+  end
+
+  # git last commit date for this {Tap}.
+  def git_last_commit_date
+    raise TapUnavailableError, name unless installed?
+    return unless git? && Utils.git_available?
+    path.cd { Utils.popen_read("git", "show", "-s", "--format=%cd", "--date=short", "HEAD").chuzzle }
+  end
+
   # The issues URL of this {Tap}.
   # e.g. `https://github.com/user/homebrew-repo/issues`
   def issues_url