feat(cli): enhance ChainListCmd with JSON output and <epoch> placeholder support

CHANGELOG.md

@@ -14,6 +14,7 @@
 - Return a `"data"` field on the `"error"` returned from RPC when `eth_call` and `eth_estimateGas` APIs encounter `execution reverted` errors. ([filecoin-project/lotus#12553](https://github.com/filecoin-project/lotus/pull/12553))
 - Implement `EthGetTransactionByBlockNumberAndIndex` (`eth_getTransactionByBlockNumberAndIndex`) and `EthGetTransactionByBlockHashAndIndex` (`eth_getTransactionByBlockHashAndIndex`) methods. ([filecoin-project/lotus#12618](https://github.com/filecoin-project/lotus/pull/12618))
 - Add a set of `lotus-shed datastore` commands for importing, exporting, and clearing parts of the datastore ([filecoin-project/lotus#12685](https://github.com/filecoin-project/lotus/pull/12685)):
+- Add json output of tipsets to `louts chain list`. ([filecoin-project/lotus#12691](https://github.com/filecoin-project/lotus/pull/12691))
 
 ## Bug Fixes
 - Fix a bug in the `lotus-shed indexes backfill-events` command that may result in either duplicate events being backfilled where there are existing events (such an operation *should* be idempotent) or events erroneously having duplicate `logIndex` values when queried via ETH APIs. ([filecoin-project/lotus#12567](https://github.com/filecoin-project/lotus/pull/12567))

cli/chain.go

@@ -581,12 +581,12 @@ var ChainListCmd = &cli.Command{
 	Aliases: []string{"love"},
 	Usage:   "View a segment of the chain",
 	Flags: []cli.Flag{
-		&cli.Uint64Flag{Name: "height", DefaultText: "current head"},
+		&cli.Uint64Flag{Name: "epoch", Aliases: []string{"height"}, DefaultText: "current head"},
 		&cli.IntFlag{Name: "count", Value: 30},
 		&cli.StringFlag{
 			Name:  "format",
-			Usage: "specify the format to print out tipsets",
-			Value: "<height>: (<time>) <blocks>",
+			Usage: "specify the format to print out tipsets using placeholders: <epoch>, <time>, <blocks>, <weight>, <tipset>, <json_tipset>\n",
+			Value: "<epoch>: (<time>) <blocks>",
 		},
 		&cli.BoolFlag{
 			Name:  "gas-stats",
@@ -932,7 +932,9 @@ func handleHamtAddress(ctx context.Context, api v0api.FullNode, r cid.Cid) error
 }
 
 func printTipSet(format string, ts *types.TipSet, afmt *AppFmt) {
-	format = strings.ReplaceAll(format, "<height>", fmt.Sprint(ts.Height()))
+	format = strings.ReplaceAll(format, "<epoch>", fmt.Sprint(ts.Height()))
+	format = strings.ReplaceAll(format, "<height>", fmt.Sprint(ts.Height())) // backwards compatibility
+
 	format = strings.ReplaceAll(format, "<time>", time.Unix(int64(ts.MinTimestamp()), 0).Format(time.Stamp))
 	blks := "[ "
 	for _, b := range ts.Blocks() {
@@ -948,6 +950,16 @@ func printTipSet(format string, ts *types.TipSet, afmt *AppFmt) {
 
 	format = strings.ReplaceAll(format, "<tipset>", strings.Join(sCids, ","))
 	format = strings.ReplaceAll(format, "<blocks>", blks)
+	if strings.Contains(format, "<json_tipset>") {
+		jsonTipset, err := json.Marshal(ts)
+		if err != nil {
+			// should not happen
+			afmt.Println("Error encoding tipset to JSON:", err)
+			return
+		}
+		format = strings.ReplaceAll(format, "<json_tipset>", string(jsonTipset))
+	}
+
 	format = strings.ReplaceAll(format, "<weight>", fmt.Sprint(ts.Blocks()[0].ParentWeight))
 
 	afmt.Println(format)

documentation/en/cli-lotus.md

@@ -1718,11 +1718,12 @@ USAGE:
    lotus chain list [command options] [arguments...]
 
 OPTIONS:
-   --height value  (default: current head)
-   --count value   (default: 30)
-   --format value  specify the format to print out tipsets (default: "<height>: (<time>) <blocks>")
-   --gas-stats     view gas statistics for the chain (default: false)
-   --help, -h      show help
+   --epoch value, --height value  (default: current head)
+   --count value                  (default: 30)
+   --format value                 specify the format to print out tipsets using placeholders: <epoch>, <time>, <blocks>, <weight>, <tipset>, <json_tipset>
+       (default: "<epoch>: (<time>) <blocks>")
+   --gas-stats  view gas statistics for the chain (default: false)
+   --help, -h   show help
 ```
 
 ### lotus chain get