run-command API: remove "env" member, always use "env_array"

Remove the "env" member from "struct child_process" in favor of always
using the "env_array". As with the preceding removal of "argv" in
favor of "args" this gets rid of current and future oddities around
memory management at the API boundary (see the amended API docs).

For some of the conversions we can replace patterns like:

    child.env = env->v;

With:

    strvec_pushv(&child.env_array, env->v);

But for others we need to guard the strvec_pushv() with a NULL check,
since we're not passing in the "v" member of a "struct strvec",
e.g. in the case of tmp_objdir_env()'s return value.

Ideally we'd rename the "env_array" member to simply "env" as a
follow-up, since it and "args" are now inconsistent in not having an
"_array" suffix, and seemingly without any good reason, unless we look
at the history of how they came to be.

But as we've currently got 122 in-tree hits for a "git grep env_array"
let's leave that for now (and possibly forever). Doing that rename
would be too disruptive.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

2 files changed, 9 insertions, 8 deletions

diff --git a/builtin/receive-pack.c b/builtin/receive-pack.c
index 48c99c8ee4..3979752cec 100644
--- a/builtin/receive-pack.c
+++ b/builtin/receive-pack.c
@@ -1367,7 +1367,7 @@ static const char *push_to_deploy(unsigned char *sha1,
 
 	strvec_pushl(&child.args, "update-index", "-q", "--ignore-submodules",
 		     "--refresh", NULL);
-	child.env = env->v;
+	strvec_pushv(&child.env_array, env->v);
 	child.dir = work_tree;
 	child.no_stdin = 1;
 	child.stdout_to_stderr = 1;
@@ -1379,7 +1379,7 @@ static const char *push_to_deploy(unsigned char *sha1,
 	child_process_init(&child);
 	strvec_pushl(&child.args, "diff-files", "--quiet",
 		     "--ignore-submodules", "--", NULL);
-	child.env = env->v;
+	strvec_pushv(&child.env_array, env->v);
 	child.dir = work_tree;
 	child.no_stdin = 1;
 	child.stdout_to_stderr = 1;
@@ -1393,7 +1393,7 @@ static const char *push_to_deploy(unsigned char *sha1,
 		     /* diff-index with either HEAD or an empty tree */
 		     head_has_history() ? "HEAD" : empty_tree_oid_hex(),
 		     "--", NULL);
-	child.env = env->v;
+	strvec_pushv(&child.env_array, env->v);
 	child.no_stdin = 1;
 	child.no_stdout = 1;
 	child.stdout_to_stderr = 0;
@@ -1404,7 +1404,7 @@ static const char *push_to_deploy(unsigned char *sha1,
 	child_process_init(&child);
 	strvec_pushl(&child.args, "read-tree", "-u", "-m", hash_to_hex(sha1),
 		     NULL);
-	child.env = env->v;
+	strvec_pushv(&child.env_array, env->v);
 	child.dir = work_tree;
 	child.no_stdin = 1;
 	child.no_stdout = 1;
@@ -2202,7 +2202,8 @@ static const char *unpack(int err_fd, struct shallow_info *si)
 			close(err_fd);
 		return "unable to create temporary object directory";
 	}
-	child.env = tmp_objdir_env(tmp_objdir);
+	if (tmp_objdir)
+		strvec_pushv(&child.env_array, tmp_objdir_env(tmp_objdir));
 
 	/*
 	 * Normally we just pass the tmp_objdir environment to the child
diff --git a/builtin/worktree.c b/builtin/worktree.c
index 9edd3e2829..962d71cf98 100644
--- a/builtin/worktree.c
+++ b/builtin/worktree.c
@@ -349,7 +349,7 @@ static int add_worktree(const char *path, const char *refname,
 			strvec_push(&cp.args, "--quiet");
 	}
 
-	cp.env = child_env.v;
+	strvec_pushv(&cp.env_array, child_env.v);
 	ret = run_command(&cp);
 	if (ret)
 		goto done;
@@ -360,7 +360,7 @@ static int add_worktree(const char *path, const char *refname,
 		strvec_pushl(&cp.args, "reset", "--hard", "--no-recurse-submodules", NULL);
 		if (opts->quiet)
 			strvec_push(&cp.args, "--quiet");
-		cp.env = child_env.v;
+		strvec_pushv(&cp.env_array, child_env.v);
 		ret = run_command(&cp);
 		if (ret)
 			goto done;
@@ -389,7 +389,7 @@ done:
 			cp.no_stdin = 1;
 			cp.stdout_to_stderr = 1;
 			cp.dir = path;
-			cp.env = env;
+			strvec_pushv(&cp.env_array, env);
 			cp.trace2_hook_name = "post-checkout";
 			strvec_pushl(&cp.args, absolute_path(hook),
 				     oid_to_hex(null_oid()),