[PATCH v1 03/11] git-gui: guard set/unset of GIT_DIR and GIT_WORK_TREE

[Mark Levedahl <mlevedahl@gmail.com>]

git-gui unconditionally exports GIT_DIR and GIT_WORK_TREE to the
environment, and furthmore unconditionally unsets these in many places.
But, GIT_WORK_TREE should be set only if it is not {} as the empty
value, really meaning no work-tree is found, causes git to throw fatal
errors (git-gui gets the error from branch --show-current).  Fixing this
is required to allow blame and browser to operate from a repository
without a worktree.

Establish a pair of functions to remove GIT_DIR and GIT_WORK_TREE from
the environment, avoiding any error if they do not exist. Also, add a
function to export these, but export GIT_WORK_TREE only if not empty.

Signed-off-by: Mark Levedahl <mlevedahl@gmail.com>
---
 git-gui.sh | 32 ++++++++++++++++++++++----------
 1 file changed, 22 insertions(+), 10 deletions(-)

diff --git a/git-gui.sh b/git-gui.sh
index a951fcd..387cad6 100755
--- a/git-gui.sh
+++ b/git-gui.sh
@@ -1122,6 +1122,22 @@ unset argv0dir
 ##
 ## repository setup
 
+proc set_gitdir_vars {} {
+	global _gitdir _gitworktree env
+	if {$_gitdir ne {}} {
+		set env(GIT_DIR) $_gitdir
+	}
+	if {$_gitworktree ne {}} {
+		set env(GIT_WORK_TREE) $_gitworktree
+	}
+}
+
+proc unset_gitdir_vars {} {
+	global env
+	catch {unset env(GIT_DIR)}
+	catch {unset env(GIT_WORK_TREE)}
+}
+
 set picked 0
 if {[catch {
 		set _gitdir $env(GIT_DIR)
@@ -1207,8 +1223,8 @@ if {[lindex $_reponame end] eq {.git}} {
 	set _reponame [lindex $_reponame end]
 }
 
-set env(GIT_DIR) $_gitdir
-set env(GIT_WORK_TREE) $_gitworktree
+# Export the final paths
+set_gitdir_vars
 
 ######################################################################
 ##
@@ -2050,13 +2066,11 @@ proc do_gitk {revs {is_submodule false}} {
 			# TODO we could make life easier (start up faster?) for gitk
 			# by setting these to the appropriate values to allow gitk
 			# to skip the heuristics to find their proper value
-			unset env(GIT_DIR)
-			unset env(GIT_WORK_TREE)
+			unset_gitdir_vars
 		}
 		safe_exec_bg [concat $cmd $revs "--" "--"]
 
-		set env(GIT_DIR) $_gitdir
-		set env(GIT_WORK_TREE) $_gitworktree
+		set_gitdir_vars
 		cd $pwd
 
 		if {[info exists main_status]} {
@@ -2084,16 +2098,14 @@ proc do_git_gui {} {
 
 		# see note in do_gitk about unsetting these vars when
 		# running tools in a submodule
-		unset env(GIT_DIR)
-		unset env(GIT_WORK_TREE)
+		unset_gitdir_vars
 
 		set pwd [pwd]
 		cd $current_diff_path
 
 		safe_exec_bg [concat $exe gui]
 
-		set env(GIT_DIR) $_gitdir
-		set env(GIT_WORK_TREE) $_gitworktree
+		set_gitdir_vars
 		cd $pwd
 
 		set status_operation [$::main_status \
-- 
2.54.0.99.14