Fall back to $EMAIL for missing GIT_AUTHOR_EMAIL and GIT_COMMITTER_EMAIL

Some other programs get the user's email address from $EMAIL, so fall back to
that if we don't have a Git-specific email address.
Signed-off-by: NJosh Triplett <josh@freedesktop.org>
Signed-off-by: NJunio C Hamano <junkio@cox.net>

Documentation/config.txt

@@ -610,8 +610,8 @@ tar.umask::
 
 user.email::
 	Your email address to be recorded in any newly created commits.
-	Can be overridden by the 'GIT_AUTHOR_EMAIL' and 'GIT_COMMITTER_EMAIL'
-	environment variables.  See gitlink:git-commit-tree[1].
+	Can be overridden by the 'GIT_AUTHOR_EMAIL', 'GIT_COMMITTER_EMAIL', and
+	'EMAIL' environment variables.  See gitlink:git-commit-tree[1].
 
 user.name::
 	Your full name to be recorded in any newly created commits.

Documentation/git-commit-tree.txt

@@ -61,6 +61,7 @@ either `.git/config` file, or using the following environment variables.
 	GIT_COMMITTER_NAME
 	GIT_COMMITTER_EMAIL
 	GIT_COMMITTER_DATE
+	EMAIL
 
 (nb "<", ">" and "\n"s are stripped)
 

Documentation/git.txt

@@ -345,6 +345,7 @@ git Commits
 'GIT_COMMITTER_NAME'::
 'GIT_COMMITTER_EMAIL'::
 'GIT_COMMITTER_DATE'::
+'EMAIL'::
 	see gitlink:git-commit-tree[1]
 
 git Diffs

ident.c

@@ -195,6 +195,8 @@ const char *fmt_ident(const char *name, const char *email,
 	setup_ident();
 	if (!name)
 		name = git_default_name;
+	if (!email)
+		email = getenv("EMAIL");
 	if (!email)
 		email = git_default_email;
 

t/test-lib.sh

@@ -16,6 +16,7 @@ unset AUTHOR_EMAIL
 unset AUTHOR_NAME
 unset COMMIT_AUTHOR_EMAIL
 unset COMMIT_AUTHOR_NAME
+unset EMAIL
 unset GIT_ALTERNATE_OBJECT_DIRECTORIES
 unset GIT_AUTHOR_DATE
 GIT_AUTHOR_EMAIL=author@example.com