8 files changed, 75 insertions, 19 deletions

diff --git a/doc/lispref/intro.texi b/doc/lispref/intro.texi
index 197f54ecc52..2353cf956cc 100644
--- a/doc/lispref/intro.texi
+++ b/doc/lispref/intro.texi
@@ -530,6 +530,18 @@ directory (without cleaning).  This is only of relevance when
 developing Emacs.
 @end defvar
 
+@defvar emacs-repository-version
+A string that gives the repository revision from which Emacs was
+built.  If Emacs was built outside revision control, the value is
+@code{nil}.
+@end defvar
+
+@defvar emacs-repository-branch
+A string that gives the repository branch from which Emacs was built.
+In the most cases this is @code{"master"}.  If Emacs was built outside
+revision control, the value is @code{nil}.
+@end defvar
+
 @node Acknowledgments
 @section Acknowledgments
 
diff --git a/etc/NEWS b/etc/NEWS
index e5892d718e8..b8073dd1752 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -225,6 +225,10 @@ In addition to nil or non-nil, the value can now be a predicate
 function.  Follow mode uses this to control scrolling of its windows
 when the last screen line in a window is not fully visible.
 
++++
+** New variable 'emacs-repository-branch'.
+It reports the git branch from which Emacs was built.
+
 
 * Editing Changes in Emacs 27.1
 
diff --git a/lisp/loadup.el b/lisp/loadup.el
index 5ecfae170fc..eb663538a3b 100644
--- a/lisp/loadup.el
+++ b/lisp/loadup.el
@@ -368,8 +368,8 @@ lost after dumping")))
                                 (string-to-number
                                  (substring name (length base) exelen))))
                              files)))
-      (setq emacs-repository-version (condition-case nil (emacs-repository-get-version)
-                              (error nil)))
+      (setq emacs-repository-version (ignore-errors (emacs-repository-get-version))
+            emacs-repository-branch (ignore-errors (emacs-repository-get-branch)))
       ;; A constant, so we shouldn't change it with `setq'.
       (defconst emacs-build-number
         (if versions (1+ (apply 'max versions)) 1))))
diff --git a/lisp/mail/emacsbug.el b/lisp/mail/emacsbug.el
index 8cacad8726d..e55f950aac3 100644
--- a/lisp/mail/emacsbug.el
+++ b/lisp/mail/emacsbug.el
@@ -307,6 +307,8 @@ usually do not have translators for other languages.\n\n")))
 
     (if (stringp emacs-repository-version)
         (insert "Repository revision: " emacs-repository-version "\n"))
+    (if (stringp emacs-repository-branch)
+        (insert "Repository branch: " emacs-repository-branch "\n"))
     (if (fboundp 'x-server-vendor)
         (condition-case nil
             ;; This is used not only for X11 but also W32 and others.
diff --git a/lisp/net/tramp-cmds.el b/lisp/net/tramp-cmds.el
index 456300e7662..3c8f182ae97 100644
--- a/lisp/net/tramp-cmds.el
+++ b/lisp/net/tramp-cmds.el
@@ -198,8 +198,9 @@ This includes password cache, file cache, connection cache, buffers."
           ;; In rare cases, it could contain the password.  So we make it nil.
           tramp-password-save-function)
       (reporter-submit-bug-report
-       tramp-bug-report-address         ; to-address
-       (format "tramp (%s)" tramp-version) ; package name and version
+       tramp-bug-report-address   ; to-address
+       (format "tramp (%s %s/%s)" ; package name and version
+               tramp-version tramp-repository-branch tramp-repository-version)
        (sort
         (delq nil (mapcar
           (lambda (x)
diff --git a/lisp/net/tramp.el b/lisp/net/tramp.el
index 44d66404f15..e8d535e85ed 100644
--- a/lisp/net/tramp.el
+++ b/lisp/net/tramp.el
@@ -1609,10 +1609,13 @@ ARGUMENTS to actually emit the message (if applicable)."
         ";; Emacs: %s Tramp: %s -*- mode: outline; -*-"
         emacs-version tramp-version))
       (when (>= tramp-verbose 10)
-        (insert
-         (format
-          "\n;; Location: %s Git: %s"
-          (locate-library "tramp") (tramp-repository-get-version)))))
+        (let ((tramp-verbose 0))
+          (insert
+           (format
+            "\n;; Location: %s Git: %s/%s"
+            (locate-library "tramp")
+            (or tramp-repository-branch "")
+            (or tramp-repository-version ""))))))
     (unless (bolp)
       (insert "\n"))
     ;; Timestamp.
diff --git a/lisp/net/trampver.el b/lisp/net/trampver.el
index de76788cc0e..f93e5380849 100644
--- a/lisp/net/trampver.el
+++ b/lisp/net/trampver.el
@@ -38,17 +38,23 @@
 (defconst tramp-bug-report-address "tramp-devel@gnu.org"
   "Email address to send bug reports to.")
 
-(defun tramp-repository-get-version ()
-  "Try to return as a string the repository revision of the Tramp sources."
-  (let ((dir (locate-dominating-file (locate-library "tramp") ".git")))
-    (when dir
-      (with-temp-buffer
-        (let ((default-directory (file-name-as-directory dir)))
-          (and (zerop
-                (ignore-errors
-                  (call-process "git" nil '(t nil) nil "rev-parse" "HEAD")))
-               (not (zerop (buffer-size)))
-               (replace-regexp-in-string "\n" "" (buffer-string))))))))
+(defconst tramp-repository-branch
+  (ignore-errors
+    ;; Suppress message from `emacs-repository-get-branch'.
+    (let ((inhibit-message t))
+      ;; `emacs-repository-get-branch' has been introduced with Emacs 27.1.
+      (with-no-warnings
+        (emacs-repository-get-branch
+         (locate-dominating-file (locate-library "tramp") ".git")))))
+  "The repository branch of the Tramp sources.")
+
+(defconst tramp-repository-version
+  (ignore-errors
+    ;; Suppress message from `emacs-repository-get-version'.
+    (let ((inhibit-message t))
+      (emacs-repository-get-version
+       (locate-dominating-file (locate-library "tramp") ".git"))))
+  "The repository revision of the Tramp sources.")
 
 ;; Check for Emacs version.
 (let ((x   (if (not (string-lessp emacs-version "24.1"))
diff --git a/lisp/version.el b/lisp/version.el
index 84919308191..c72164cdacc 100644
--- a/lisp/version.el
+++ b/lisp/version.el
@@ -135,6 +135,34 @@ Optional argument DIR is a directory to use instead of `source-directory'.
 Optional argument EXTERNAL is ignored."
   (emacs-repository-version-git (or dir source-directory)))
 
+(defvar emacs-repository-branch nil
+  "String giving the repository branch from which this Emacs was built.
+Value is nil if Emacs was not built from a repository checkout,
+or if we could not determine the branch.")
+
+(defun emacs-repository-branch-git (dir)
+  "Ask git itself for the branch information for directory DIR."
+  (message "Waiting for git...")
+  (with-temp-buffer
+    (let ((default-directory (file-name-as-directory dir)))
+      (and (zerop
+            (with-demoted-errors "Error running git rev-parse --abbrev-ref: %S"
+              (call-process "git" nil '(t nil) nil
+                            "rev-parse" "--abbrev-ref" "HEAD")))
+           (goto-char (point-min))
+           (buffer-substring (point) (line-end-position))))))
+
+(defun emacs-repository-get-branch (&optional dir)
+  "Try to return as a string the repository branch of the Emacs sources.
+The format of the returned string is dependent on the VCS in use.
+Value is nil if the sources do not seem to be under version
+control, or if we could not determine the branch.  Note that
+this reports on the current state of the sources, which may not
+correspond to the running Emacs.
+
+Optional argument DIR is a directory to use instead of `source-directory'."
+  (emacs-repository-branch-git (or dir source-directory)))
+
 ;; We put version info into the executable in the form that `ident' uses.
 (purecopy (concat "\n$Id: " (subst-char-in-string ?\n ?\s (emacs-version))
                   " $\n"))