feat(cli): support multiple env file argument (#26527)

Closes #26425 

## Overview

This PR adds support for specifying multiple environment files as
arguments when using the Deno CLI. Subsequent files override
pre-existing variables defined in previous files.

If the same variable is defined in the environment and in the file, the
value from the environment takes precedence.

## Example Usage
```bash
deno run --allow-env --env-file --env-file=".env.one" --env-file=".env.two" script.ts
```

---------

Co-authored-by: Bartek Iwańczuk <biwanczuk@gmail.com>

12 files changed, 47 insertions, 8 deletions

diff --git a/tests/specs/run/env_file/__test__.jsonc b/tests/specs/run/env_file/__test__.jsonc
new file mode 100644
index 000000000..642062169
--- /dev/null
+++ b/tests/specs/run/env_file/__test__.jsonc
@@ -0,0 +1,20 @@
+{
+  "tests": {
+    "basic": {
+      "args": "run --env=./env --allow-env env_file.ts",
+      "output": "env_file.out"
+    },
+    "missing": {
+      "args": "run --env=./missing --allow-env env_file.ts",
+      "output": "env_file_missing.out"
+    },
+    "multiple": {
+      "args": "run --env=./env --env=./env_one --env=./env_two --allow-env env_file.ts",
+      "output": "multiple_env_file.out"
+    },
+    "unparseable": {
+      "args": "run --env=./env_unparseable --allow-env env_file.ts",
+      "output": "env_unparseable.out"
+    }
+  }
+}
diff --git a/tests/specs/run/env_file/env b/tests/specs/run/env_file/env
new file mode 100644
index 000000000..c41732d30
--- /dev/null
+++ b/tests/specs/run/env_file/env
@@ -0,0 +1,4 @@
+FOO=BAR
+ANOTHER_FOO=ANOTHER_${FOO}
+MULTILINE="First Line
+Second Line"
\ No newline at end of file
diff --git a/tests/specs/run/env_file/env_file.out b/tests/specs/run/env_file/env_file.out
new file mode 100644
index 000000000..54a0bf25d
--- /dev/null
+++ b/tests/specs/run/env_file/env_file.out
@@ -0,0 +1,4 @@
+BAR
+ANOTHER_BAR
+First Line
+Second Line
diff --git a/tests/specs/run/env_unparsable_file/main.js b/tests/specs/run/env_file/env_file.ts
index 48488ce72..48488ce72 100644
--- a/tests/specs/run/env_unparsable_file/main.js
+++ b/tests/specs/run/env_file/env_file.ts
diff --git a/tests/specs/run/env_file/env_file_missing.out b/tests/specs/run/env_file/env_file_missing.out
new file mode 100644
index 000000000..34b2bf810
--- /dev/null
+++ b/tests/specs/run/env_file/env_file_missing.out
@@ -0,0 +1,4 @@
+Warning The `--env-file` flag was used, but the environment file specified './missing' was not found.
+undefined
+undefined
+undefined
diff --git a/tests/specs/run/env_file/env_one b/tests/specs/run/env_file/env_one
new file mode 100644
index 000000000..c26038a67
--- /dev/null
+++ b/tests/specs/run/env_file/env_one
@@ -0,0 +1,2 @@
+FOO=BARBAR
+ANOTHER_FOO=OVERRIDEN_BY_ENV_ONE
diff --git a/tests/specs/run/env_file/env_two b/tests/specs/run/env_file/env_two
new file mode 100644
index 000000000..fe8392c3a
--- /dev/null
+++ b/tests/specs/run/env_file/env_two
@@ -0,0 +1 @@
+FOO=OVERRIDEN_BY_ENV_TWO
diff --git a/tests/specs/run/env_file/env_unparseable b/tests/specs/run/env_file/env_unparseable
new file mode 100644
index 000000000..5542b80bc
--- /dev/null
+++ b/tests/specs/run/env_file/env_unparseable
@@ -0,0 +1,4 @@
+FOO=valid
+ANOTHER_FOO=c:\path
+MULTILINE="First Line
+Second Line"
\ No newline at end of file
diff --git a/tests/specs/run/env_file/env_unparseable.out b/tests/specs/run/env_file/env_unparseable.out
new file mode 100644
index 000000000..0a88d164e
--- /dev/null
+++ b/tests/specs/run/env_file/env_unparseable.out
@@ -0,0 +1,4 @@
+Warning Parsing failed within the specified environment file: ./env_unparseable at index: 3 of the value: c:\path
+valid
+undefined
+undefined
diff --git a/tests/specs/run/env_file/multiple_env_file.out b/tests/specs/run/env_file/multiple_env_file.out
new file mode 100644
index 000000000..3fa97d599
--- /dev/null
+++ b/tests/specs/run/env_file/multiple_env_file.out
@@ -0,0 +1,4 @@
+OVERRIDEN_BY_ENV_TWO
+OVERRIDEN_BY_ENV_ONE
+First Line
+Second Line
diff --git a/tests/specs/run/env_unparsable_file/__test__.jsonc b/tests/specs/run/env_unparsable_file/__test__.jsonc
deleted file mode 100644
index bed150635..000000000
--- a/tests/specs/run/env_unparsable_file/__test__.jsonc
+++ /dev/null
@@ -1,4 +0,0 @@
-{
-  "args": "run --env=../../../testdata/env_unparsable --allow-env main.js",
-  "output": "main.out"
-}
diff --git a/tests/specs/run/env_unparsable_file/main.out b/tests/specs/run/env_unparsable_file/main.out
deleted file mode 100644
index a19ff4dd6..000000000
--- a/tests/specs/run/env_unparsable_file/main.out
+++ /dev/null
@@ -1,4 +0,0 @@
-Warning Parsing failed within the specified environment file: ../../../testdata/env_unparsable at index: 3 of the value: c:\path
-valid
-undefined
-undefined