ref: dump and copy edit exp branch Example

from https://github.com/iterative/dvc.org/pull/1926/files#diff-cc5af77c4ee8049c6726817aff466e2908f7a54b4435524d5a0fe2059bd48f9d

content/docs/command-reference/exp/branch.md

@@ -48,3 +48,44 @@ To switch into the new branch, use `git checkout branch` and `dvc checkout`.
 
 - `-v`, `--verbose` - displays detailed tracing information from executing the
   `dvc pull` command.
+
+## Example: Make a persistent branch from an experiment
+
+> This example is based on our
+> [Get Started](/doc/tutorials/get-started/experiments), where you can find the
+> actual source code.
+
+Let's say we have run 3 experiments in our project:
+
+```dvc
+$ dvc exp show --include-params=featurize
+┏━━━━━━━━━━━━━━━━━━━━━━━┳━━━━━━━━━━━━━━┳━━━━━━━━━┳━━━━━━━━━━━━━━━━━━━━━━━━┳━━━━━━━━━━━━━━━━━━┓
+┃ Experiment            ┃ Created      ┃     auc ┃ featurize.max_features ┃ featurize.ngrams ┃
+┡━━━━━━━━━━━━━━━━━━━━━━━╇━━━━━━━━━━━━━━╇━━━━━━━━━╇━━━━━━━━━━━━━━━━━━━━━━━━╇━━━━━━━━━━━━━━━━━━┩
+│ workspace             │ -            │ 0.61314 │ 1500                   │ 2                │
+│ 11-bigrams-experiment │ Jun 20, 2020 │ 0.61314 │ 1500                   │ 2                │
+│ ├── exp-e6c97         │ Oct 21, 2020 │ 0.61314 │ 1500                   │ 2                │
+│ ├── exp-1dad0         │ Oct 09, 2020 │ 0.57756 │ 2000                   │ 2                │
+│ └── exp-1df77         │ Oct 09, 2020 │ 0.51676 │ 500                    │ 2                │
+└───────────────────────┴──────────────┴─────────┴────────────────────────┴──────────────────┘
+```
+
+We may want to branch-off `exp-1dad0` for a separate experimentation process
+(based on 2000 `max_features`).
+
+```dvc
+$ dvc exp branch exp-1dad0 maxf-2000
+Git branch 'maxf-2000' has been created from experiment 'exp-1dad0'.
+To switch to the new branch run:
+        git checkout my-branch
+```
+
+We can inspect the result with Git:
+
+```dvc
+$ git branch
+* master
+  maxf-2000
+```
+
+`maxf-2000` can now be merged, rebased, pushed, etc. like any other Git branch.