feat(skip): allow overriding config skip codecs

Add --skip-codec-override so users can ignore configured skip codecs for
a single run and use only codecs provided through --skip-codec.

Defer CLI skip-codec parsing until after config loading so the final
skip list can be resolved independently of option order.

Document the new override behavior in the README and man page, and add
shell completion for the new flag.

4 files changed, 61 insertions, 12 deletions

diff --git a/README.md b/README.md
index 32f6a0c..ab9a569 100644
--- a/README.md
+++ b/README.md
@@ -134,9 +134,11 @@ An optional TOML configuration file can be placed at:
 ${XDG_CONFIG_HOME:-$HOME/.config}/transcode.sh/config.toml
 ```
 
-Use `--config-file FILE` to load an alternative path. CLI flags always take
-precedence over values in the config file. The file must be valid TOML — an
-unparseable file is a hard error. Requires `tomlq` when the file is present.
+Use `--config-file FILE` to load an alternative path. CLI flags generally take
+precedence over values in the config file. Skip codecs are additive by default:
+configured codecs and CLI codecs are merged unless `--skip-codec-override` is
+used. The file must be valid TOML — an unparseable file is a hard error.
+Requires `tomlq` when the file is present.
 
 **Example `config.toml`:**
 
@@ -169,10 +171,12 @@ quiet   = false
 | `[output]` | `verbose` | boolean | `-v` |
 | `[size_report]` | `enabled` | boolean | `-s` / `--no-size-report` |
 | `[size_report]` | `file` | string | `--size-report-file` |
-| `[skip]` | `codecs` | array of strings | `-S` (merged with CLI) |
+| `[skip]` | `codecs` | array of strings | `-S` / `--skip-codec-override` |
 
 > **Note:** `[skip] codecs` from the config file and `--skip-codec` from the
-> CLI are **merged** — both sources contribute to the skip list.
+> CLI are **merged** by default — both sources contribute to the skip list. Use
+> `--skip-codec-override` to ignore configured skip codecs and use only codecs
+> provided through `--skip-codec` for that run.
 
 > **Note:** `[encoding] hwaccel` accepts `false` (disable), `true` (use `auto`),
 > or a method string such as `"vaapi"` or `"cuda"`. CLI `--hwaccel`/`--no-hwaccel`
@@ -209,7 +213,8 @@ transcode.sh [OPTION] [--] FILE...
 | `-s`, `--size-report` | Print per-file size feedback and write a status TSV log |
 | `--no-size-report` | Disable a size report enabled in `config.toml` |
 | `--size-report-file PATH`, `--size-report-file=PATH` | Size report TSV path (default: `transcode_size_report`) |
-| `-S LIST`, `--skip-codec LIST`, `--skip-codec=LIST` | Codecs to skip (comma/space/colon separated) |
+| `-S LIST`, `--skip-codec LIST`, `--skip-codec=LIST` | Add codecs to the effective skip list (comma/space/colon separated) |
+| `--skip-codec-override` | Use only codecs from `--skip-codec`, ignoring `[skip].codecs` from config |
 | `-l`, `--only-if-smaller` | Only replace original if new file is smaller |
 | `--no-only-if-smaller` | Do replace original even if new file is bigger |
 | `-p NAME`, `--preset NAME`, `--preset=NAME` | Preset to use (default: `default`) |
@@ -238,6 +243,9 @@ transcode.sh --backup-dir ~/transcode-backups *.mp4
 # Use a custom preset, only keep result if smaller, skip AV1 inputs
 transcode.sh --preset av1_fast --only-if-smaller --skip-codec av1 /media/films/*.mkv
 
+# Temporarily replace the configured skip list with only HEVC
+transcode.sh --skip-codec-override --skip-codec hevc input.mkv
+
 # Run at a moderate priority and continue past failures
 transcode.sh --nice 10 --continue *.mp4
 
diff --git a/transcode.sh b/transcode.sh
index 3290596..dc6da41 100755
--- a/transcode.sh
+++ b/transcode.sh
@@ -188,6 +188,8 @@ _CLI_SIZE_REPORT=0
 _CLI_SIZE_REPORT_FILE=0
 _CLI_VERBOSE=0
 _CLI_VERIFY_OUTPUT=0
+_CLI_SKIP_CODECS_OVERRIDE=0
+_CLI_SKIP_CODECS=()
 
 # Values for size report
 _REPORT_ENCODING_FAILED=0
@@ -299,6 +301,8 @@ ${BOLD}${BLUE}Input options:${ALL_OFF}
   ${BOLD}${YELLOW}-f, --encode-file${ALL_OFF} ${BOLD}${GREEN}FILE${ALL_OFF}        file containing a list of files to encode
   ${BOLD}${YELLOW}-S, --skip-codec${ALL_OFF} ${BOLD}${GREEN}LIST${ALL_OFF}         skip files with these codecs;
                                 ${BOLD}${GREEN}LIST${ALL_OFF} is comma, space, or colon separated
+      ${BOLD}${YELLOW}--skip-codec-override${ALL_OFF}     use only codecs from --skip-codec,
+                                ignoring [skip].codecs from config
 
 ${BOLD}${BLUE}Size report options:${ALL_OFF}
   ${BOLD}${YELLOW}-s, --size-report${ALL_OFF}             print size feedback and write a status TSV log
@@ -1553,11 +1557,15 @@ while [[ $# -gt 0 ]]; do
       error "Missing value for $1"
       exit $EXIT_USAGE_ERROR
     fi
-    parse_skip_codec_parameter "$2"
+    _CLI_SKIP_CODECS+=("$2")
     shift 2
     ;;
   --skip-codec=*)
-    parse_skip_codec_parameter "${1#*=}"
+    _CLI_SKIP_CODECS+=("${1#*=}")
+    shift
+    ;;
+  --skip-codec-override)
+    _CLI_SKIP_CODECS_OVERRIDE=1
     shift
     ;;
   -l | --only-if-smaller)
@@ -1640,6 +1648,14 @@ done
 # are set, but before validation so config-supplied values are validated too.
 load_config
 
+if [[ $_CLI_SKIP_CODECS_OVERRIDE -eq 1 ]]; then
+  SKIP_CODECS=()
+fi
+
+for codec_list in "${_CLI_SKIP_CODECS[@]}"; do
+  parse_skip_codec_parameter "$codec_list"
+done
+
 printf -v joined ' %s' "${!SKIP_CODECS[@]}"
 
 debug "Effective configuration:"
diff --git a/transcode.sh.1 b/transcode.sh.1
index c827336..2dd725a 100644
--- a/transcode.sh.1
+++ b/transcode.sh.1
@@ -151,12 +151,22 @@ in the current working directory.
 .BR \-S " \fILIST\fR, " \-\-skip\-codec " \fILIST\fR, " \-\-skip\-codec= \fILIST\fR
 Comma-, space- or colon-separated list of video codec names to skip.
 Files whose detected input codec appears in this list are left untouched.
-Codecs specified here are merged with any codecs listed under
+By default, codecs specified here are merged with any codecs listed under
 .B [skip] codecs
 in
 .B config.toml
 \(em both sources contribute to the skip list.
 .TP
+.BR \-\-skip\-codec\-override
+Ignore codecs listed under
+.B [skip] codecs
+in
+.B config.toml
+and use only codecs provided through
+.BR \-S / \-\-skip\-codec
+for this run. The position of this flag on the command line does not matter;
+it changes how the final skip list is resolved after all options are parsed.
+.TP
 .BR \-l ", " \-\-only\-if\-smaller
 After encoding, replace the original only when the new file is strictly
 smaller. If the transcoded file is larger the temporary file is removed
@@ -358,8 +368,10 @@ sources.
 .TP
 .IR "${XDG_CONFIG_HOME:-$HOME/.config}/transcode.sh/config.toml"
 Optional TOML configuration file. Provides defaults for all options.
-CLI flags always take precedence. The file must be valid TOML; an
-unparseable file is a hard error. Requires
+CLI flags generally take precedence. Skip codecs are additive by default:
+configured codecs and CLI codecs are merged unless
+.BR \-\-skip\-codec\-override
+is used. The file must be valid TOML; an unparseable file is a hard error. Requires
 .BR tomlq (1).
 Supported sections and keys:
 .RS
@@ -400,7 +412,11 @@ CLI \fB--backup-dir\fR takes precedence.
 .TP
 .B [skip] codecs
 Array of strings. Merged with any codecs from
-.BR \-S .
+.BR \-S
+by default. Use
+.BR \-\-skip\-codec\-override
+to ignore this configured list and use only codecs provided through
+.BR \-S / \-\-skip\-codec .
 .TP
 .B [size_report] enabled
 Boolean. Equivalent to
@@ -492,6 +508,14 @@ transcode.sh \-N 10 \-S av1 input.mkv
 .fi
 .RE
 .PP
+Temporarily replace configured skip codecs with only HEVC:
+.PP
+.RS
+.nf
+transcode.sh \-\-skip\-codec\-override \-S hevc input.mkv
+.fi
+.RE
+.PP
 Load an alternative configuration file:
 .PP
 .RS
diff --git a/transcode.sh.bash-completion b/transcode.sh.bash-completion
index 7a0529d..ea3bf74 100644
--- a/transcode.sh.bash-completion
+++ b/transcode.sh.bash-completion
@@ -167,6 +167,7 @@ _transcode_sh() {
       --size-report-file=
       --skip-codec
       --skip-codec=
+      --skip-codec-override
       --verbose
       --verify-output
       --version