Repository: iterative/dvc

Issue:
exp show: wrong params display after params modified.
# Bug Report

![image](https://user-images.githubusercontent.com/6745454/114495175-37a7e980-9c50-11eb-83ab-c24bbaf3c8e5.png)
![image](https://user-images.githubusercontent.com/6745454/114495217-468e9c00-9c50-11eb-9798-9db3f3d3ed1c.png)

Same exp branches with different shown values in branch `exp-44136`.

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## Issue name

Issue names must follow the pattern `command: description` where the command is the dvc command that you are trying to run. The description should describe the consequence of the bug. 

Example: `repro: doesn't detect input changes`
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## Description

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### Reproduce

1. delete some params, both in `dvc.yaml` and `params.yaml`. Delete fields or slots, not the values.
2. dvc exp run
3. dvc exp show
4. dvc exp apply <newly add exp branch>
5. dvc exp show

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Step list of how to reproduce the bug
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Example:

1. dvc init
2. Copy dataset.zip to the directory
3. dvc add dataset.zip
4. dvc run -d dataset.zip -o model ./train.sh
5. modify dataset.zip
6. dvc repro
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### Expected

Params value to be consistent in `dvc exp show`.

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### Environment information
```
DVC version: 2.0.17+353e4c
---------------------------------
Platform: Python 3.8.5 on Linux-5.4.0-70-generic-x86_64-with-glibc2.29
Supports: All remotes
Cache types: hardlink, symlink
Cache directory: xfs on /dev/sda2
Caches: local
Remotes: None
Workspace directory: xfs on /dev/sda2
Repo: dvc, git
```
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**Output of `dvc doctor`:**

```console
$ dvc doctor
```

**Additional Information (if any):**

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Discussion:
@karajan1001 can you include an actual reproduction script here? It's not clear what exactly you are modifying and applying
@pmrowla 
```
 $ git init
 $ dvc init
 $ git commit -m "init"
 $ echo '{"acc":0.90}' > acc
 $ dvc run -d acc -m result.json -n copy "cat acc>result.json"
 $ git add dvc.lock .gitignore dvc.yaml
 $ git commit -m "first version"
 $ dvc exp run -f
 $ echo 'lr: 0.01' > params.yaml
 $ vim dvc.yaml # add lr to field params
 $ echo '{"acc":0.95}' > acc
 $ dvc exp run
 $ dvc exp show
 $ dvc exp apply exp-d2074 # here to the old version in dvc exp show
 $ dvc exp show
```

Resolving patch:
diff --git a/dvc/repo/experiments/show.py b/dvc/repo/experiments/show.py
--- a/dvc/repo/experiments/show.py
+++ b/dvc/repo/experiments/show.py
@@ -13,11 +13,13 @@
 
 
 def _collect_experiment_commit(
-    repo, rev, stash=False, sha_only=True, param_deps=False
+    repo, exp_rev, stash=False, sha_only=True, param_deps=False
 ):
     res = defaultdict(dict)
-    for rev in repo.brancher(revs=[rev]):
+    for rev in repo.brancher(revs=[exp_rev]):
         if rev == "workspace":
+            if exp_rev != "workspace":
+                continue
             res["timestamp"] = None
         else:
             commit = repo.scm.resolve_commit(rev)


Test patch: