Merge branch 'ps/config-env-pairs'

Introduce two new ways to feed configuration variable-value pairs
via environment variables, and tweak the way GIT_CONFIG_PARAMETERS
encodes variable/value pairs to make it more robust.

* ps/config-env-pairs:
  config: allow specifying config entries via envvar pairs
  environment: make `getenv_safe()` a public function
  config: store "git -c" variables using more robust format
  config: parse more robust format in GIT_CONFIG_PARAMETERS
  config: extract function to parse config pairs
  quote: make sq_dequote_step() a public function
  config: add new way to pass config via `--config-env`
  git: add `--super-prefix` to usage string

11 files changed, 491 insertions, 39 deletions

diff --git a/Documentation/git-config.txt b/Documentation/git-config.txt
index 0e9351d3cb..4b4cc5c5e8 100644
--- a/Documentation/git-config.txt
+++ b/Documentation/git-config.txt
@@ -346,6 +346,22 @@ GIT_CONFIG_NOSYSTEM::
 
 See also <<FILES>>.
 
+GIT_CONFIG_COUNT::
+GIT_CONFIG_KEY_<n>::
+GIT_CONFIG_VALUE_<n>::
+	If GIT_CONFIG_COUNT is set to a positive number, all environment pairs
+	GIT_CONFIG_KEY_<n> and GIT_CONFIG_VALUE_<n> up to that number will be
+	added to the process's runtime configuration. The config pairs are
+	zero-indexed. Any missing key or value is treated as an error. An empty
+	GIT_CONFIG_COUNT is treated the same as GIT_CONFIG_COUNT=0, namely no
+	pairs are processed. These environment variables will override values
+	in configuration files, but will be overridden by any explicit options
+	passed via `git -c`.
++
+This is useful for cases where you want to spawn multiple git commands
+with a common configuration but cannot depend on a configuration file,
+for example when writing scripts.
+
 
 [[EXAMPLES]]
 EXAMPLES
diff --git a/Documentation/git.txt b/Documentation/git.txt
index a6d4ad0818..d36e6fd482 100644
--- a/Documentation/git.txt
+++ b/Documentation/git.txt
@@ -13,7 +13,7 @@ SYNOPSIS
     [--exec-path[=<path>]] [--html-path] [--man-path] [--info-path]
     [-p|--paginate|-P|--no-pager] [--no-replace-objects] [--bare]
     [--git-dir=<path>] [--work-tree=<path>] [--namespace=<name>]
-    [--super-prefix=<path>]
+    [--super-prefix=<path>] [--config-env <name>=<envvar>]
     <command> [<args>]
 
 DESCRIPTION
@@ -80,6 +80,28 @@ config file). Including the equals but with an empty value (like `git -c
 foo.bar= ...`) sets `foo.bar` to the empty string which `git config
 --type=bool` will convert to `false`.
 
+--config-env=<name>=<envvar>::
+	Like `-c <name>=<value>`, give configuration variable
+	'<name>' a value, where <envvar> is the name of an
+	environment variable from which to retrieve the value. Unlike
+	`-c` there is no shortcut for directly setting the value to an
+	empty string, instead the environment variable itself must be
+	set to the empty string.  It is an error if the `<envvar>` does not exist
+	in the environment. `<envvar>` may not contain an equals sign
+	to avoid ambiguity with `<name>`s which contain one.
++
+This is useful for cases where you want to pass transitory
+configuration options to git, but are doing so on OS's where
+other processes might be able to read your cmdline
+(e.g. `/proc/self/cmdline`), but not your environ
+(e.g. `/proc/self/environ`). That behavior is the default on
+Linux, but may not be on your system.
++
+Note that this might add security for variables such as
+`http.extraHeader` where the sensitive information is part of
+the value, but not e.g. `url.<base>.insteadOf` where the
+sensitive information can be part of the key.
+
 --exec-path[=<path>]::
 	Path to wherever your core Git programs are installed.
 	This can also be controlled by setting the GIT_EXEC_PATH
diff --git a/cache.h b/cache.h
index eefa93b08f..f22d12ecb0 100644
--- a/cache.h
+++ b/cache.h
@@ -472,6 +472,7 @@ static inline enum object_type object_type(unsigned int mode)
 #define TEMPLATE_DIR_ENVIRONMENT "GIT_TEMPLATE_DIR"
 #define CONFIG_ENVIRONMENT "GIT_CONFIG"
 #define CONFIG_DATA_ENVIRONMENT "GIT_CONFIG_PARAMETERS"
+#define CONFIG_COUNT_ENVIRONMENT "GIT_CONFIG_COUNT"
 #define EXEC_PATH_ENVIRONMENT "GIT_EXEC_PATH"
 #define CEILING_DIRECTORIES_ENVIRONMENT "GIT_CEILING_DIRECTORIES"
 #define NO_REPLACE_OBJECTS_ENVIRONMENT "GIT_NO_REPLACE_OBJECTS"
diff --git a/config.c b/config.c
index 4c0cf3a1c1..f5068231bd 100644
--- a/config.c
+++ b/config.c
@@ -8,6 +8,7 @@
 #include "cache.h"
 #include "branch.h"
 #include "config.h"
+#include "environment.h"
 #include "repository.h"
 #include "lockfile.h"
 #include "exec-cmd.h"
@@ -332,7 +333,7 @@ int git_config_include(const char *var, const char *value, void *data)
 	return ret;
 }
 
-void git_config_push_parameter(const char *text)
+static void git_config_push_split_parameter(const char *key, const char *value)
 {
 	struct strbuf env = STRBUF_INIT;
 	const char *old = getenv(CONFIG_DATA_ENVIRONMENT);
@@ -340,11 +341,74 @@ void git_config_push_parameter(const char *text)
 		strbuf_addstr(&env, old);
 		strbuf_addch(&env, ' ');
 	}
-	sq_quote_buf(&env, text);
+	sq_quote_buf(&env, key);
+	strbuf_addch(&env, '=');
+	if (value)
+		sq_quote_buf(&env, value);
 	setenv(CONFIG_DATA_ENVIRONMENT, env.buf, 1);
 	strbuf_release(&env);
 }
 
+void git_config_push_parameter(const char *text)
+{
+	const char *value;
+
+	/*
+	 * When we see:
+	 *
+	 *   section.subsection=with=equals.key=value
+	 *
+	 * we cannot tell if it means:
+	 *
+	 *   [section "subsection=with=equals"]
+	 *   key = value
+	 *
+	 * or:
+	 *
+	 *   [section]
+	 *   subsection = with=equals.key=value
+	 *
+	 * We parse left-to-right for the first "=", meaning we'll prefer to
+	 * keep the value intact over the subsection. This is historical, but
+	 * also sensible since values are more likely to contain odd or
+	 * untrusted input than a section name.
+	 *
+	 * A missing equals is explicitly allowed (as a bool-only entry).
+	 */
+	value = strchr(text, '=');
+	if (value) {
+		char *key = xmemdupz(text, value - text);
+		git_config_push_split_parameter(key, value + 1);
+		free(key);
+	} else {
+		git_config_push_split_parameter(text, NULL);
+	}
+}
+
+void git_config_push_env(const char *spec)
+{
+	char *key;
+	const char *env_name;
+	const char *env_value;
+
+	env_name = strrchr(spec, '=');
+	if (!env_name)
+		die(_("invalid config format: %s"), spec);
+	key = xmemdupz(spec, env_name - spec);
+	env_name++;
+	if (!*env_name)
+		die(_("missing environment variable name for configuration '%.*s'"),
+		    (int)(env_name - spec - 1), spec);
+
+	env_value = getenv(env_name);
+	if (!env_value)
+		die(_("missing environment variable '%s' for configuration '%.*s'"),
+		    env_name, (int)(env_name - spec - 1), spec);
+
+	git_config_push_split_parameter(key, env_value);
+	free(key);
+}
+
 static inline int iskeychar(int c)
 {
 	return isalnum(c) || c == '-';
@@ -437,11 +501,26 @@ int git_config_key_is_valid(const char *key)
 	return !git_config_parse_key_1(key, NULL, NULL, 1);
 }
 
+static int config_parse_pair(const char *key, const char *value,
+			  config_fn_t fn, void *data)
+{
+	char *canonical_name;
+	int ret;
+
+	if (!strlen(key))
+		return error(_("empty config key"));
+	if (git_config_parse_key(key, &canonical_name, NULL))
+		return -1;
+
+	ret = (fn(canonical_name, value, data) < 0) ? -1 : 0;
+	free(canonical_name);
+	return ret;
+}
+
 int git_config_parse_parameter(const char *text,
 			       config_fn_t fn, void *data)
 {
 	const char *value;
-	char *canonical_name;
 	struct strbuf **pair;
 	int ret;
 
@@ -462,51 +541,131 @@ int git_config_parse_parameter(const char *text,
 		return error(_("bogus config parameter: %s"), text);
 	}
 
-	if (git_config_parse_key(pair[0]->buf, &canonical_name, NULL)) {
-		ret = -1;
-	} else {
-		ret = (fn(canonical_name, value, data) < 0) ? -1 : 0;
-		free(canonical_name);
-	}
+	ret = config_parse_pair(pair[0]->buf, value, fn, data);
 	strbuf_list_free(pair);
 	return ret;
 }
 
+static int parse_config_env_list(char *env, config_fn_t fn, void *data)
+{
+	char *cur = env;
+	while (cur && *cur) {
+		const char *key = sq_dequote_step(cur, &cur);
+		if (!key)
+			return error(_("bogus format in %s"),
+				     CONFIG_DATA_ENVIRONMENT);
+
+		if (!cur || isspace(*cur)) {
+			/* old-style 'key=value' */
+			if (git_config_parse_parameter(key, fn, data) < 0)
+				return -1;
+		}
+		else if (*cur == '=') {
+			/* new-style 'key'='value' */
+			const char *value;
+
+			cur++;
+			if (*cur == '\'') {
+				/* quoted value */
+				value = sq_dequote_step(cur, &cur);
+				if (!value || (cur && !isspace(*cur))) {
+					return error(_("bogus format in %s"),
+						     CONFIG_DATA_ENVIRONMENT);
+				}
+			} else if (!*cur || isspace(*cur)) {
+				/* implicit bool: 'key'= */
+				value = NULL;
+			} else {
+				return error(_("bogus format in %s"),
+					     CONFIG_DATA_ENVIRONMENT);
+			}
+
+			if (config_parse_pair(key, value, fn, data) < 0)
+				return -1;
+		}
+		else {
+			/* unknown format */
+			return error(_("bogus format in %s"),
+				     CONFIG_DATA_ENVIRONMENT);
+		}
+
+		if (cur) {
+			while (isspace(*cur))
+				cur++;
+		}
+	}
+	return 0;
+}
+
 int git_config_from_parameters(config_fn_t fn, void *data)
 {
-	const char *env = getenv(CONFIG_DATA_ENVIRONMENT);
+	const char *env;
+	struct strbuf envvar = STRBUF_INIT;
+	struct strvec to_free = STRVEC_INIT;
 	int ret = 0;
-	char *envw;
-	const char **argv = NULL;
-	int nr = 0, alloc = 0;
-	int i;
+	char *envw = NULL;
 	struct config_source source;
 
-	if (!env)
-		return 0;
-
 	memset(&source, 0, sizeof(source));
 	source.prev = cf;
 	source.origin_type = CONFIG_ORIGIN_CMDLINE;
 	cf = &source;
 
-	/* sq_dequote will write over it */
-	envw = xstrdup(env);
+	env = getenv(CONFIG_COUNT_ENVIRONMENT);
+	if (env) {
+		unsigned long count;
+		char *endp;
+		int i;
 
-	if (sq_dequote_to_argv(envw, &argv, &nr, &alloc) < 0) {
-		ret = error(_("bogus format in %s"), CONFIG_DATA_ENVIRONMENT);
-		goto out;
+		count = strtoul(env, &endp, 10);
+		if (*endp) {
+			ret = error(_("bogus count in %s"), CONFIG_COUNT_ENVIRONMENT);
+			goto out;
+		}
+		if (count > INT_MAX) {
+			ret = error(_("too many entries in %s"), CONFIG_COUNT_ENVIRONMENT);
+			goto out;
+		}
+
+		for (i = 0; i < count; i++) {
+			const char *key, *value;
+
+			strbuf_addf(&envvar, "GIT_CONFIG_KEY_%d", i);
+			key = getenv_safe(&to_free, envvar.buf);
+			if (!key) {
+				ret = error(_("missing config key %s"), envvar.buf);
+				goto out;
+			}
+			strbuf_reset(&envvar);
+
+			strbuf_addf(&envvar, "GIT_CONFIG_VALUE_%d", i);
+			value = getenv_safe(&to_free, envvar.buf);
+			if (!value) {
+				ret = error(_("missing config value %s"), envvar.buf);
+				goto out;
+			}
+			strbuf_reset(&envvar);
+
+			if (config_parse_pair(key, value, fn, data) < 0) {
+				ret = -1;
+				goto out;
+			}
+		}
 	}
 
-	for (i = 0; i < nr; i++) {
-		if (git_config_parse_parameter(argv[i], fn, data) < 0) {
+	env = getenv(CONFIG_DATA_ENVIRONMENT);
+	if (env) {
+		/* sq_dequote will write over it */
+		envw = xstrdup(env);
+		if (parse_config_env_list(envw, fn, data) < 0) {
 			ret = -1;
 			goto out;
 		}
 	}
 
 out:
-	free(argv);
+	strbuf_release(&envvar);
+	strvec_clear(&to_free);
 	free(envw);
 	cf = source.prev;
 	return ret;
diff --git a/config.h b/config.h
index c1449bb790..19a9adbaa9 100644
--- a/config.h
+++ b/config.h
@@ -138,6 +138,7 @@ int git_config_from_mem(config_fn_t fn,
 int git_config_from_blob_oid(config_fn_t fn, const char *name,
 			     const struct object_id *oid, void *data);
 void git_config_push_parameter(const char *text);
+void git_config_push_env(const char *spec);
 int git_config_from_parameters(config_fn_t fn, void *data);
 void read_early_config(config_fn_t cb, void *data);
 void read_very_early_config(config_fn_t cb, void *data);
diff --git a/environment.c b/environment.c
index bb518c61cd..2f27008424 100644
--- a/environment.c
+++ b/environment.c
@@ -9,6 +9,7 @@
  */
 #include "cache.h"
 #include "branch.h"
+#include "environment.h"
 #include "repository.h"
 #include "config.h"
 #include "refs.h"
@@ -116,6 +117,7 @@ const char * const local_repo_env[] = {
 	ALTERNATE_DB_ENVIRONMENT,
 	CONFIG_ENVIRONMENT,
 	CONFIG_DATA_ENVIRONMENT,
+	CONFIG_COUNT_ENVIRONMENT,
 	DB_ENVIRONMENT,
 	GIT_DIR_ENVIRONMENT,
 	GIT_WORK_TREE_ENVIRONMENT,
@@ -152,11 +154,7 @@ static char *expand_namespace(const char *raw_namespace)
 	return strbuf_detach(&buf, NULL);
 }
 
-/*
- * Wrapper of getenv() that returns a strdup value. This value is kept
- * in argv to be freed later.
- */
-static const char *getenv_safe(struct strvec *argv, const char *name)
+const char *getenv_safe(struct strvec *argv, const char *name)
 {
 	const char *value = getenv(name);
 
diff --git a/environment.h b/environment.h
new file mode 100644
index 0000000000..d438b5c8f3
--- /dev/null
+++ b/environment.h
@@ -0,0 +1,12 @@
+#ifndef ENVIRONMENT_H
+#define ENVIRONMENT_H
+
+#include "strvec.h"
+
+/*
+ * Wrapper of getenv() that returns a strdup value. This value is kept
+ * in argv to be freed later.
+ */
+const char *getenv_safe(struct strvec *argv, const char *name);
+
+#endif
diff --git a/git.c b/git.c
index a00a0a4d94..b5f63d346b 100644
--- a/git.c
+++ b/git.c
@@ -29,6 +29,7 @@ const char git_usage_string[] =
 	   "           [--exec-path[=<path>]] [--html-path] [--man-path] [--info-path]\n"
 	   "           [-p | --paginate | -P | --no-pager] [--no-replace-objects] [--bare]\n"
 	   "           [--git-dir=<path>] [--work-tree=<path>] [--namespace=<name>]\n"
+	   "           [--super-prefix=<path>] [--config-env=<name>=<envvar>]\n"
 	   "           <command> [<args>]");
 
 const char git_more_info_string[] =
@@ -254,6 +255,8 @@ static int handle_options(const char ***argv, int *argc, int *envchanged)
 			git_config_push_parameter((*argv)[1]);
 			(*argv)++;
 			(*argc)--;
+		} else if (skip_prefix(cmd, "--config-env=", &cmd)) {
+			git_config_push_env(cmd);
 		} else if (!strcmp(cmd, "--literal-pathspecs")) {
 			setenv(GIT_LITERAL_PATHSPECS_ENVIRONMENT, "1", 1);
 			if (envchanged)
diff --git a/quote.c b/quote.c
index 69f4ca45da..8a3a5e39eb 100644
--- a/quote.c
+++ b/quote.c
@@ -116,7 +116,7 @@ void sq_append_quote_argv_pretty(struct strbuf *dst, const char **argv)
 	}
 }
 
-static char *sq_dequote_step(char *arg, char **next)
+char *sq_dequote_step(char *arg, char **next)
 {
 	char *dst = arg;
 	char *src = arg;
@@ -153,11 +153,8 @@ static char *sq_dequote_step(char *arg, char **next)
 			}
 		/* Fallthrough */
 		default:
-			if (!next || !isspace(*src))
+			if (!next)
 				return NULL;
-			do {
-				c = *++src;
-			} while (isspace(c));
 			*dst = 0;
 			*next = src;
 			return arg;
@@ -182,6 +179,14 @@ static int sq_dequote_to_argv_internal(char *arg,
 		char *dequoted = sq_dequote_step(next, &next);
 		if (!dequoted)
 			return -1;
+		if (next) {
+			char c;
+			if (!isspace(*next))
+				return -1;
+			do {
+				c = *++next;
+			} while (isspace(c));
+		}
 		if (argv) {
 			ALLOC_GROW(*argv, *nr + 1, *alloc);
 			(*argv)[(*nr)++] = dequoted;
diff --git a/quote.h b/quote.h
index 4b72a583cf..768cc6338e 100644
--- a/quote.h
+++ b/quote.h
@@ -42,13 +42,27 @@ void sq_quote_buf_pretty(struct strbuf *, const char *src);
 void sq_quote_argv_pretty(struct strbuf *, const char **argv);
 void sq_append_quote_argv_pretty(struct strbuf *dst, const char **argv);
 
-/* This unwraps what sq_quote() produces in place, but returns
+/*
+ * This unwraps what sq_quote() produces in place, but returns
  * NULL if the input does not look like what sq_quote would have
- * produced.
+ * produced (the full string must be a single quoted item).
  */
 char *sq_dequote(char *);
 
 /*
+ * Like sq_dequote(), but dequote a single item, and leave "next" pointing to
+ * the next character. E.g., in the string:
+ *
+ *   'one' 'two' 'three'
+ *
+ * after the first call, the return value would be the unquoted string "one",
+ * with "next" pointing to the space between "one" and "two"). The caller is
+ * responsible for advancing the pointer to the start of the next item before
+ * calling sq_dequote_step() again.
+ */
+char *sq_dequote_step(char *src, char **next);
+
+/*
  * Same as the above, but can be used to unwrap many arguments in the
  * same string separated by space. Like sq_quote, it works in place,
  * modifying arg and appending pointers into it to argv.
diff --git a/t/t1300-config.sh b/t/t1300-config.sh
index e745b29c16..936d72041b 100755
--- a/t/t1300-config.sh
+++ b/t/t1300-config.sh
@@ -1289,6 +1289,58 @@ test_expect_success 'git -c is not confused by empty environment' '
 	GIT_CONFIG_PARAMETERS="" git -c x.one=1 config --list
 '
 
+test_expect_success 'GIT_CONFIG_PARAMETERS handles old-style entries' '
+	v="${SQ}key.one=foo${SQ}" &&
+	v="$v  ${SQ}key.two=bar${SQ}" &&
+	v="$v ${SQ}key.ambiguous=section.whatever=value${SQ}" &&
+	GIT_CONFIG_PARAMETERS=$v git config --get-regexp "key.*" >actual &&
+	cat >expect <<-EOF &&
+	key.one foo
+	key.two bar
+	key.ambiguous section.whatever=value
+	EOF
+	test_cmp expect actual
+'
+
+test_expect_success 'GIT_CONFIG_PARAMETERS handles new-style entries' '
+	v="${SQ}key.one${SQ}=${SQ}foo${SQ}" &&
+	v="$v  ${SQ}key.two${SQ}=${SQ}bar${SQ}" &&
+	v="$v ${SQ}key.ambiguous=section.whatever${SQ}=${SQ}value${SQ}" &&
+	GIT_CONFIG_PARAMETERS=$v git config --get-regexp "key.*" >actual &&
+	cat >expect <<-EOF &&
+	key.one foo
+	key.two bar
+	key.ambiguous=section.whatever value
+	EOF
+	test_cmp expect actual
+'
+
+test_expect_success 'old and new-style entries can mix' '
+	v="${SQ}key.oldone=oldfoo${SQ}" &&
+	v="$v ${SQ}key.newone${SQ}=${SQ}newfoo${SQ}" &&
+	v="$v ${SQ}key.oldtwo=oldbar${SQ}" &&
+	v="$v ${SQ}key.newtwo${SQ}=${SQ}newbar${SQ}" &&
+	GIT_CONFIG_PARAMETERS=$v git config --get-regexp "key.*" >actual &&
+	cat >expect <<-EOF &&
+	key.oldone oldfoo
+	key.newone newfoo
+	key.oldtwo oldbar
+	key.newtwo newbar
+	EOF
+	test_cmp expect actual
+'
+
+test_expect_success 'old and new bools with ambiguous subsection' '
+	v="${SQ}key.with=equals.oldbool${SQ}" &&
+	v="$v ${SQ}key.with=equals.newbool${SQ}=" &&
+	GIT_CONFIG_PARAMETERS=$v git config --get-regexp "key.*" >actual &&
+	cat >expect <<-EOF &&
+	key.with equals.oldbool
+	key.with=equals.newbool
+	EOF
+	test_cmp expect actual
+'
+
 test_expect_success 'detect bogus GIT_CONFIG_PARAMETERS' '
 	cat >expect <<-\EOF &&
 	env.one one
@@ -1311,6 +1363,173 @@ test_expect_success 'detect bogus GIT_CONFIG_PARAMETERS' '
 		git config --get-regexp "env.*"
 '
 
+test_expect_success 'git --config-env=key=envvar support' '
+	cat >expect <<-\EOF &&
+	value
+	value
+	false
+	EOF
+	{
+		ENVVAR=value git --config-env=core.name=ENVVAR config core.name &&
+		ENVVAR=value git --config-env=foo.CamelCase=ENVVAR config foo.camelcase &&
+		ENVVAR= git --config-env=foo.flag=ENVVAR config --bool foo.flag
+	} >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'git --config-env fails with invalid parameters' '
+	test_must_fail git --config-env=foo.flag config --bool foo.flag 2>error &&
+	test_i18ngrep "invalid config format: foo.flag" error &&
+	test_must_fail git --config-env=foo.flag= config --bool foo.flag 2>error &&
+	test_i18ngrep "missing environment variable name for configuration ${SQ}foo.flag${SQ}" error &&
+	sane_unset NONEXISTENT &&
+	test_must_fail git --config-env=foo.flag=NONEXISTENT config --bool foo.flag 2>error &&
+	test_i18ngrep "missing environment variable ${SQ}NONEXISTENT${SQ} for configuration ${SQ}foo.flag${SQ}" error
+'
+
+test_expect_success 'git -c and --config-env work together' '
+	cat >expect <<-\EOF &&
+	bar.cmd cmd-value
+	bar.env env-value
+	EOF
+	ENVVAR=env-value git \
+		-c bar.cmd=cmd-value \
+		--config-env=bar.env=ENVVAR \
+		config --get-regexp "^bar.*" >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'git -c and --config-env override each other' '
+	cat >expect <<-\EOF &&
+	env
+	cmd
+	EOF
+	{
+		ENVVAR=env git -c bar.bar=cmd --config-env=bar.bar=ENVVAR config bar.bar &&
+		ENVVAR=env git --config-env=bar.bar=ENVVAR -c bar.bar=cmd config bar.bar
+	} >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success '--config-env handles keys with equals' '
+	echo value=with=equals >expect &&
+	ENVVAR=value=with=equals git \
+		--config-env=section.subsection=with=equals.key=ENVVAR \
+		config section.subsection=with=equals.key >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'git config handles environment config pairs' '
+	GIT_CONFIG_COUNT=2 \
+		GIT_CONFIG_KEY_0="pair.one" GIT_CONFIG_VALUE_0="foo" \
+		GIT_CONFIG_KEY_1="pair.two" GIT_CONFIG_VALUE_1="bar" \
+		git config --get-regexp "pair.*" >actual &&
+	cat >expect <<-EOF &&
+	pair.one foo
+	pair.two bar
+	EOF
+	test_cmp expect actual
+'
+
+test_expect_success 'git config ignores pairs without count' '
+	test_must_fail env GIT_CONFIG_KEY_0="pair.one" GIT_CONFIG_VALUE_0="value" \
+		git config pair.one 2>error &&
+	test_must_be_empty error
+'
+
+test_expect_success 'git config ignores pairs with zero count' '
+	test_must_fail env \
+		GIT_CONFIG_COUNT=0 \
+		GIT_CONFIG_KEY_0="pair.one" GIT_CONFIG_VALUE_0="value" \
+		git config pair.one
+'
+
+test_expect_success 'git config ignores pairs exceeding count' '
+	GIT_CONFIG_COUNT=1 \
+		GIT_CONFIG_KEY_0="pair.one" GIT_CONFIG_VALUE_0="value" \
+		GIT_CONFIG_KEY_1="pair.two" GIT_CONFIG_VALUE_1="value" \
+		git config --get-regexp "pair.*" >actual &&
+	cat >expect <<-EOF &&
+	pair.one value
+	EOF
+	test_cmp expect actual
+'
+
+test_expect_success 'git config ignores pairs with zero count' '
+	test_must_fail env \
+		GIT_CONFIG_COUNT=0 GIT_CONFIG_KEY_0="pair.one" GIT_CONFIG_VALUE_0="value" \
+		git config pair.one >error &&
+	test_must_be_empty error
+'
+
+test_expect_success 'git config ignores pairs with empty count' '
+	test_must_fail env \
+		GIT_CONFIG_COUNT= GIT_CONFIG_KEY_0="pair.one" GIT_CONFIG_VALUE_0="value" \
+		git config pair.one >error &&
+	test_must_be_empty error
+'
+
+test_expect_success 'git config fails with invalid count' '
+	test_must_fail env GIT_CONFIG_COUNT=10a git config --list 2>error &&
+	test_i18ngrep "bogus count" error &&
+	test_must_fail env GIT_CONFIG_COUNT=9999999999999999 git config --list 2>error &&
+	test_i18ngrep "too many entries" error
+'
+
+test_expect_success 'git config fails with missing config key' '
+	test_must_fail env GIT_CONFIG_COUNT=1 GIT_CONFIG_VALUE_0="value" \
+		git config --list 2>error &&
+	test_i18ngrep "missing config key" error
+'
+
+test_expect_success 'git config fails with missing config value' '
+	test_must_fail env GIT_CONFIG_COUNT=1 GIT_CONFIG_KEY_0="pair.one" \
+		git config --list 2>error &&
+	test_i18ngrep "missing config value" error
+'
+
+test_expect_success 'git config fails with invalid config pair key' '
+	test_must_fail env GIT_CONFIG_COUNT=1 \
+		GIT_CONFIG_KEY_0= GIT_CONFIG_VALUE_0=value \
+		git config --list &&
+	test_must_fail env GIT_CONFIG_COUNT=1 \
+		GIT_CONFIG_KEY_0=missing-section GIT_CONFIG_VALUE_0=value \
+		git config --list
+'
+
+test_expect_success 'environment overrides config file' '
+	test_when_finished "rm -f .git/config" &&
+	cat >.git/config <<-EOF &&
+	[pair]
+	one = value
+	EOF
+	GIT_CONFIG_COUNT=1 GIT_CONFIG_KEY_0=pair.one GIT_CONFIG_VALUE_0=override \
+		git config pair.one >actual &&
+	cat >expect <<-EOF &&
+	override
+	EOF
+	test_cmp expect actual
+'
+
+test_expect_success 'GIT_CONFIG_PARAMETERS overrides environment config' '
+	GIT_CONFIG_COUNT=1 GIT_CONFIG_KEY_0=pair.one GIT_CONFIG_VALUE_0=value \
+		GIT_CONFIG_PARAMETERS="${SQ}pair.one=override${SQ}" \
+		git config pair.one >actual &&
+	cat >expect <<-EOF &&
+	override
+	EOF
+	test_cmp expect actual
+'
+
+test_expect_success 'command line overrides environment config' '
+	GIT_CONFIG_COUNT=1 GIT_CONFIG_KEY_0=pair.one GIT_CONFIG_VALUE_0=value \
+		git -c pair.one=override config pair.one >actual &&
+	cat >expect <<-EOF &&
+	override
+	EOF
+	test_cmp expect actual
+'
+
 test_expect_success 'git config --edit works' '
 	git config -f tmp test.value no &&
 	echo test.value=yes >expect &&
@@ -1656,9 +1875,11 @@ test_expect_success '--show-origin with --list' '
 	file:.git/config	user.override=local
 	file:.git/config	include.path=../include/relative.include
 	file:.git/../include/relative.include	user.relative=include
+	command line:	user.environ=true
 	command line:	user.cmdline=true
 	EOF
-	git -c user.cmdline=true config --list --show-origin >output &&
+	GIT_CONFIG_COUNT=1 GIT_CONFIG_KEY_0=user.environ GIT_CONFIG_VALUE_0=true\
+		git -c user.cmdline=true config --list --show-origin >output &&
 	test_cmp expect output
 '