fix(config): make every config key environment-overridable

docs/user/04-configuration.md

@@ -504,27 +504,14 @@ Environment variables use the prefix `DOT_` followed by the section-qualified ke
 by single underscores, uppercased. For example `symlinks.mode` becomes `DOT_SYMLINKS_MODE`. There is
 no double-underscore convention.
 
-Only the following keys are bound:
-
-```
-DOT_DIRECTORIES_PACKAGE   DOT_DIRECTORIES_TARGET   DOT_DIRECTORIES_MANIFEST
-DOT_LOGGING_LEVEL         DOT_LOGGING_FORMAT       DOT_LOGGING_DESTINATION   DOT_LOGGING_FILE
-DOT_SYMLINKS_MODE         DOT_SYMLINKS_FOLDING     DOT_SYMLINKS_OVERWRITE
-DOT_SYMLINKS_BACKUP       DOT_SYMLINKS_BACKUP_SUFFIX
-DOT_IGNORE_USE_DEFAULTS   DOT_IGNORE_PATTERNS      DOT_IGNORE_OVERRIDES
-DOT_IGNORE_PER_PACKAGE_IGNORE   DOT_IGNORE_MAX_FILE_SIZE   DOT_IGNORE_INTERACTIVE_LARGE_FILES
-DOT_DOTFILE_TRANSLATE     DOT_DOTFILE_PREFIX
-DOT_OUTPUT_FORMAT         DOT_OUTPUT_COLOR         DOT_OUTPUT_PROGRESS
-DOT_OUTPUT_VERBOSITY      DOT_OUTPUT_WIDTH
-DOT_OPERATIONS_DRY_RUN    DOT_OPERATIONS_ATOMIC    DOT_OPERATIONS_MAX_PARALLEL
-DOT_PACKAGES_SORT_BY      DOT_PACKAGES_AUTO_DISCOVER   DOT_PACKAGES_VALIDATE_NAMES
-DOT_DOCTOR_AUTO_FIX       DOT_DOCTOR_CHECK_MANIFEST    DOT_DOCTOR_CHECK_BROKEN_LINKS
-DOT_DOCTOR_CHECK_ORPHANED DOT_DOCTOR_CHECK_PERMISSIONS
-DOT_EXPERIMENTAL_PARALLEL DOT_EXPERIMENTAL_PROFILING
-```
-
-`symlinks.backup_dir`, `dotfile.package_name_mapping`, `output.table_style`, and every key under
-`update` and `network` have no environment binding; set them in the configuration file.
+Every configuration key in the tables above is bound: `DOT_` plus the uppercased key with `.`
+replaced by `_`. `symlinks.backup_dir` becomes `DOT_SYMLINKS_BACKUP_DIR`,
+`dotfile.package_name_mapping` becomes `DOT_DOTFILE_PACKAGE_NAME_MAPPING`, and the `update` and
+`network` sections follow the same rule. An environment value overrides the configuration file even
+when it sets a boolean to `false`.
+
+Path-typed values (`directories.*`, `symlinks.backup_dir`, `logging.file`) expand `~` and `$VAR`
+references exactly as file values do.
 
 `DOT_CONFIG` is handled separately and overrides the configuration file path.
 

docs/user/08-troubleshooting.md

@@ -310,9 +310,10 @@ dot manage dot-vim     # Uses config file
 dot -v manage dot-vim  # -v overrides config
 ```
 
-Not every key is bound to an environment variable. `symlinks.backup_dir`,
-`dotfile.package_name_mapping`, `output.table_style`, and the whole `update`
-and `network` sections have no environment binding.
+Every configuration key is bound to an environment variable: `DOT_` plus the
+uppercased key with dots replaced by underscores, including `symlinks.backup_dir`,
+`dotfile.package_name_mapping`, `output.table_style`, and the `update` and
+`network` sections.
 
 ### Invalid Configuration
 

internal/config/expand.go

@@ -35,16 +35,7 @@ import (
 // On error the configuration is left as written, and the message names both
 // the offending key and the reference that could not be resolved.
 func (c *ExtendedConfig) ExpandPaths() error {
-	fields := []struct {
-		key   string
-		value *string
-	}{
-		{"directories.package", &c.Directories.Package},
-		{"directories.target", &c.Directories.Target},
-		{"directories.manifest", &c.Directories.Manifest},
-		{"symlinks.backup_dir", &c.Symlinks.BackupDir},
-		{"logging.file", &c.Logging.File},
-	}
+	fields := c.pathFields()
 
 	expanded := make([]string, len(fields))
 	for i, field := range fields {
@@ -62,6 +53,25 @@ func (c *ExtendedConfig) ExpandPaths() error {
 	return nil
 }
 
+// pathField pairs a path-typed configuration key with its value slot.
+type pathField struct {
+	key   string
+	value *string
+}
+
+// pathFields returns every path-typed configuration value in a stable order.
+// It is the single list both ExpandPaths and the environment override path
+// consume, so a new path-typed field is expanded everywhere or nowhere.
+func (c *ExtendedConfig) pathFields() []pathField {
+	return []pathField{
+		{"directories.package", &c.Directories.Package},
+		{"directories.target", &c.Directories.Target},
+		{"directories.manifest", &c.Directories.Manifest},
+		{"symlinks.backup_dir", &c.Symlinks.BackupDir},
+		{"logging.file", &c.Logging.File},
+	}
+}
+
 // expandPath expands environment variables and a leading tilde in a single
 // path value. An empty value stays empty, so callers can distinguish "unset"
 // from "set to the home directory".