Provide a build time default-editor setting

Provide a DEFAULT_EDITOR knob to allow setting the fallback
editor to use instead of vi (when VISUAL, EDITOR, and GIT_EDITOR
are unset).  The value can be set at build time according to a
system’s policy.  For example, on Debian systems, the default
editor should be the 'editor' command.

Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Ben Walton <bwalton@artsci.utoronto.ca>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Makefile

@@ -200,6 +200,14 @@ all::
 # memory allocators with the nedmalloc allocator written by Niall Douglas.
 #
 # Define NO_REGEX if you have no or inferior regex support in your C library.
+#
+# Define DEFAULT_EDITOR to a sensible editor command (defaults to "vi") if you
+# want to use something different.  The value will be interpreted by the shell
+# if necessary when it is used.  Examples:
+#
+#   DEFAULT_EDITOR='~/bin/vi',
+#   DEFAULT_EDITOR='$GIT_FALLBACK_EDITOR',
+#   DEFAULT_EDITOR='"C:\Program Files\Vim\gvim.exe" --nofork'
 
 GIT-VERSION-FILE: .FORCE-GIT-VERSION-FILE
 	@$(SHELL_PATH) ./GIT-VERSION-GEN
@@ -1363,6 +1371,15 @@ BASIC_CFLAGS += -DSHA1_HEADER='$(SHA1_HEADER_SQ)' \
 	$(COMPAT_CFLAGS)
 LIB_OBJS += $(COMPAT_OBJS)
 
+# Quote for C
+
+ifdef DEFAULT_EDITOR
+DEFAULT_EDITOR_CQ = "$(subst ",\",$(subst \,\\,$(DEFAULT_EDITOR)))"
+DEFAULT_EDITOR_CQ_SQ = $(subst ','\'',$(DEFAULT_EDITOR_CQ))
+
+BASIC_CFLAGS += -DDEFAULT_EDITOR='$(DEFAULT_EDITOR_CQ_SQ)'
+endif
+
 ALL_CFLAGS += $(BASIC_CFLAGS)
 ALL_LDFLAGS += $(BASIC_LDFLAGS)
 

editor.c

@@ -2,6 +2,10 @@
 #include "strbuf.h"
 #include "run-command.h"
 
+#ifndef DEFAULT_EDITOR
+#define DEFAULT_EDITOR "vi"
+#endif
+
 const char *git_editor(void)
 {
 	const char *editor = getenv("GIT_EDITOR");
@@ -19,7 +23,7 @@ const char *git_editor(void)
 		return NULL;
 
 	if (!editor)
-		editor = "vi";
+		editor = DEFAULT_EDITOR;
 
 	return editor;
 }

t/t7005-editor.sh

@@ -4,27 +4,40 @@ test_description='GIT_EDITOR, core.editor, and stuff'
 
 . ./test-lib.sh
 
-for i in GIT_EDITOR core_editor EDITOR VISUAL vi
+unset EDITOR VISUAL GIT_EDITOR
+
+test_expect_success 'determine default editor' '
+
+	vi=$(TERM=vt100 git var GIT_EDITOR) &&
+	test -n "$vi"
+
+'
+
+if ! expr "$vi" : '^[a-z]*$' >/dev/null
+then
+	vi=
+fi
+
+for i in GIT_EDITOR core_editor EDITOR VISUAL $vi
 do
 	cat >e-$i.sh <<-EOF
 	#!$SHELL_PATH
 	echo "Edited by $i" >"\$1"
 	EOF
 	chmod +x e-$i.sh
 done
-unset vi
-mv e-vi.sh vi
-unset EDITOR VISUAL GIT_EDITOR
+
+if ! test -z "$vi"
+then
+	mv e-$vi.sh $vi
+fi
 
 test_expect_success setup '
 
-	msg="Hand edited" &&
+	msg="Hand-edited" &&
+	test_commit "$msg" &&
 	echo "$msg" >expect &&
-	git add vi &&
-	test_tick &&
-	git commit -m "$msg" &&
-	git show -s --pretty=oneline |
-	sed -e "s/^[0-9a-f]* //" >actual &&
+	git show -s --format=%s > actual &&
 	diff actual expect
 
 '
@@ -54,7 +67,7 @@ test_expect_success 'dumb should prefer EDITOR to VISUAL' '
 
 TERM=vt100
 export TERM
-for i in vi EDITOR VISUAL core_editor GIT_EDITOR
+for i in $vi EDITOR VISUAL core_editor GIT_EDITOR
 do
 	echo "Edited by $i" >expect
 	unset EDITOR VISUAL GIT_EDITOR
@@ -78,7 +91,7 @@ done
 
 unset EDITOR VISUAL GIT_EDITOR
 git config --unset-all core.editor
-for i in vi EDITOR VISUAL core_editor GIT_EDITOR
+for i in $vi EDITOR VISUAL core_editor GIT_EDITOR
 do
 	echo "Edited by $i" >expect
 	case "$i" in