From e91b338191c6c58803ce84e8e04c318715bd0e6c Mon Sep 17 00:00:00 2001
From: Rod Vagg <rod@vagg.org>
Date: Thu, 17 Oct 2024 12:08:55 +1100
Subject: [PATCH] feat(cli): lotus chain head --height to print epoch number

A simpler version of what's currently possible with:

	lotus chain list --format '<height>' --count 1
---
 CHANGELOG.md                  |  3 +--
 cli/chain.go                  | 14 ++++++++++++--
 documentation/en/cli-lotus.md |  1 +
 3 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 47ecf7d0768..e287a49148b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,7 @@
 - Reduce size of embedded genesis CAR files by removing WASM actor blocks and compressing with zstd. This reduces the `lotus` binary size by approximately 10 MiB. ([filecoin-project/lotus#12439](https://github.com/filecoin-project/lotus/pull/12439))
 - Add ChainSafe operated Calibration archival node to the bootstrap list ([filecoin-project/lotus#12517](https://github.com/filecoin-project/lotus/pull/12517))
 - Fix hotloop in F3 pariticpation API ([filecoin-project/lotus#12575](https://github.com/filecoin-project/lotus/pull/12575))
+- `lotus chain head` now supports a `--height` flag to print just the epoch number of the current chain head ([filecoin-project/lotus#12609](https://github.com/filecoin-project/lotus/pull/12609))
 
 ## 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))
@@ -15,8 +16,6 @@
 
 ## Improvements
 
-## Improvements
-
 ## Deps
 
 # UNRELEASED Node v1.30.0  
diff --git a/cli/chain.go b/cli/chain.go
index f941061d5d9..e04a715ac1e 100644
--- a/cli/chain.go
+++ b/cli/chain.go
@@ -72,6 +72,12 @@ var ChainCmd = &cli.Command{
 var ChainHeadCmd = &cli.Command{
 	Name:  "head",
 	Usage: "Print chain head",
+	Flags: []cli.Flag{
+		&cli.BoolFlag{
+			Name:  "height",
+			Usage: "print just the epoch number of the chain head",
+		},
+	},
 	Action: func(cctx *cli.Context) error {
 		afmt := NewAppFmt(cctx.App)
 
@@ -87,8 +93,12 @@ var ChainHeadCmd = &cli.Command{
 			return err
 		}
 
-		for _, c := range head.Cids() {
-			afmt.Println(c)
+		if cctx.Bool("height") {
+			afmt.Println(head.Height())
+		} else {
+			for _, c := range head.Cids() {
+				afmt.Println(c)
+			}
 		}
 		return nil
 	},
diff --git a/documentation/en/cli-lotus.md b/documentation/en/cli-lotus.md
index 7ec4f78a930..02950a2ba56 100644
--- a/documentation/en/cli-lotus.md
+++ b/documentation/en/cli-lotus.md
@@ -1616,6 +1616,7 @@ USAGE:
    lotus chain head [command options] [arguments...]
 
 OPTIONS:
+   --height    print just the epoch number of the chain head (default: false)
    --help, -h  show help
 ```